diff --git a/docs/custom_llm.md b/docs/custom_llm.md
new file mode 100644
index 000000000..245aa3ca4
--- /dev/null
+++ b/docs/custom_llm.md
@@ -0,0 +1,225 @@
+# Custom LLM Implementations
+
+CrewAI now supports custom LLM implementations through the `BaseLLM` abstract base class. This allows you to create your own LLM implementations that don't rely on litellm's authentication mechanism.
+
+## Using Custom LLM Implementations
+
+To create a custom LLM implementation, you need to:
+
+1. Inherit from the `BaseLLM` abstract base class
+2. Implement the required methods:
+   - `call()`: The main method to call the LLM with messages
+   - `supports_function_calling()`: Whether the LLM supports function calling
+   - `supports_stop_words()`: Whether the LLM supports stop words
+   - `get_context_window_size()`: The context window size of the LLM
+
+## Example: Basic Custom LLM
+
+```python
+from crewai import BaseLLM
+from typing import Any, Dict, List, Optional, Union
+
+class CustomLLM(BaseLLM):
+    def __init__(self, api_key: str, endpoint: str):
+        super().__init__()  # Initialize the base class to set default attributes
+        self.api_key = api_key
+        self.endpoint = endpoint
+        self.stop = []  # You can customize stop words if needed
+        
+    def call(
+        self,
+        messages: Union[str, List[Dict[str, str]]],
+        tools: Optional[List[dict]] = None,
+        callbacks: Optional[List[Any]] = None,
+        available_functions: Optional[Dict[str, Any]] = None,
+    ) -> Union[str, Any]:
+        # Implement your own logic to call the LLM
+        # For example, using requests:
+        import requests
+        
+        headers = {
+            "Authorization": f"Bearer {self.api_key}",
+            "Content-Type": "application/json"
+        }
+        
+        # Convert string message to proper format if needed
+        if isinstance(messages, str):
+            messages = [{"role": "user", "content": messages}]
+        
+        data = {
+            "messages": messages,
+            "tools": tools
+        }
+        
+        response = requests.post(self.endpoint, headers=headers, json=data)
+        return response.json()["choices"][0]["message"]["content"]
+        
+    def supports_function_calling(self) -> bool:
+        # Return True if your LLM supports function calling
+        return True
+        
+    def supports_stop_words(self) -> bool:
+        # Return True if your LLM supports stop words
+        return True
+        
+    def get_context_window_size(self) -> int:
+        # Return the context window size of your LLM
+        return 8192
+```
+
+## Example: JWT-based Authentication
+
+For services that use JWT-based authentication instead of API keys, you can implement a custom LLM like this:
+
+```python
+from crewai import BaseLLM, Agent, Task
+from typing import Any, Dict, List, Optional, Union
+
+class JWTAuthLLM(BaseLLM):
+    def __init__(self, jwt_token: str, endpoint: str):
+        super().__init__()  # Initialize the base class to set default attributes
+        self.jwt_token = jwt_token
+        self.endpoint = endpoint
+        self.stop = []  # You can customize stop words if needed
+        
+    def call(
+        self,
+        messages: Union[str, List[Dict[str, str]]],
+        tools: Optional[List[dict]] = None,
+        callbacks: Optional[List[Any]] = None,
+        available_functions: Optional[Dict[str, Any]] = None,
+    ) -> Union[str, Any]:
+        # Implement your own logic to call the LLM with JWT authentication
+        import requests
+        
+        headers = {
+            "Authorization": f"Bearer {self.jwt_token}",
+            "Content-Type": "application/json"
+        }
+        
+        # Convert string message to proper format if needed
+        if isinstance(messages, str):
+            messages = [{"role": "user", "content": messages}]
+        
+        data = {
+            "messages": messages,
+            "tools": tools
+        }
+        
+        response = requests.post(self.endpoint, headers=headers, json=data)
+        return response.json()["choices"][0]["message"]["content"]
+        
+    def supports_function_calling(self) -> bool:
+        # Return True if your LLM supports function calling
+        return True
+        
+    def supports_stop_words(self) -> bool:
+        # Return True if your LLM supports stop words
+        return True
+        
+    def get_context_window_size(self) -> int:
+        # Return the context window size of your LLM
+        return 8192
+```
+
+## Using Your Custom LLM with CrewAI
+
+Once you've implemented your custom LLM, you can use it with CrewAI agents and crews:
+
+```python
+# Create your custom LLM instance
+jwt_llm = JWTAuthLLM(
+    jwt_token="your.jwt.token", 
+    endpoint="https://your-llm-endpoint.com/v1/chat/completions"
+)
+
+# Use it with an agent
+agent = Agent(
+    role="Research Assistant",
+    goal="Find information on a topic",
+    backstory="You are a research assistant tasked with finding information.",
+    llm=jwt_llm,
+)
+
+# Create a task for the agent
+task = Task(
+    description="Research the benefits of exercise",
+    agent=agent,
+    expected_output="A summary of the benefits of exercise",
+)
+
+# Execute the task
+result = agent.execute_task(task)
+print(result)
+```
+
+## Advanced Usage: Function Calling
+
+If your LLM supports function calling, you can implement the function calling logic in your custom LLM:
+
+```python
+def call(
+    self,
+    messages: Union[str, List[Dict[str, str]]],
+    tools: Optional[List[dict]] = None,
+    callbacks: Optional[List[Any]] = None,
+    available_functions: Optional[Dict[str, Any]] = None,
+) -> Union[str, Any]:
+    import requests
+    
+    headers = {
+        "Authorization": f"Bearer {self.jwt_token}",
+        "Content-Type": "application/json"
+    }
+    
+    # Convert string message to proper format if needed
+    if isinstance(messages, str):
+        messages = [{"role": "user", "content": messages}]
+    
+    data = {
+        "messages": messages,
+        "tools": tools
+    }
+    
+    response = requests.post(self.endpoint, headers=headers, json=data)
+    response_data = response.json()
+    
+    # Check if the LLM wants to call a function
+    if response_data["choices"][0]["message"].get("tool_calls"):
+        tool_calls = response_data["choices"][0]["message"]["tool_calls"]
+        
+        # Process each tool call
+        for tool_call in tool_calls:
+            function_name = tool_call["function"]["name"]
+            function_args = json.loads(tool_call["function"]["arguments"])
+            
+            if available_functions and function_name in available_functions:
+                function_to_call = available_functions[function_name]
+                function_response = function_to_call(**function_args)
+                
+                # Add the function response to the messages
+                messages.append({
+                    "role": "tool",
+                    "tool_call_id": tool_call["id"],
+                    "name": function_name,
+                    "content": str(function_response)
+                })
+        
+        # Call the LLM again with the updated messages
+        return self.call(messages, tools, callbacks, available_functions)
+    
+    # Return the text response if no function call
+    return response_data["choices"][0]["message"]["content"]
+```
+
+## Implementing Your Own Authentication Mechanism
+
+The `BaseLLM` class allows you to implement any authentication mechanism you need, not just JWT or API keys. You can use:
+
+- OAuth tokens
+- Client certificates
+- Custom headers
+- Session-based authentication
+- Any other authentication method required by your LLM provider
+
+Simply implement the appropriate authentication logic in your custom LLM class.
diff --git a/src/crewai/__init__.py b/src/crewai/__init__.py
index 662af2563..ca5b9ccb7 100644
--- a/src/crewai/__init__.py
+++ b/src/crewai/__init__.py
@@ -4,7 +4,7 @@ from crewai.agent import Agent
 from crewai.crew import Crew
 from crewai.flow.flow import Flow
 from crewai.knowledge.knowledge import Knowledge
-from crewai.llm import LLM
+from crewai.llm import BaseLLM, LLM
 from crewai.process import Process
 from crewai.task import Task
 
@@ -21,6 +21,7 @@ __all__ = [
     "Process",
     "Task",
     "LLM",
+    "BaseLLM",
     "Flow",
     "Knowledge",
 ]
diff --git a/src/crewai/agent.py b/src/crewai/agent.py
index cfebc18e5..fe1f829e9 100644
--- a/src/crewai/agent.py
+++ b/src/crewai/agent.py
@@ -11,7 +11,7 @@ from crewai.agents.crew_agent_executor import CrewAgentExecutor
 from crewai.knowledge.knowledge import Knowledge
 from crewai.knowledge.source.base_knowledge_source import BaseKnowledgeSource
 from crewai.knowledge.utils.knowledge_utils import extract_knowledge_context
-from crewai.llm import LLM
+from crewai.llm import BaseLLM, LLM
 from crewai.memory.contextual.contextual_memory import ContextualMemory
 from crewai.task import Task
 from crewai.tools import BaseTool
@@ -70,10 +70,10 @@ class Agent(BaseAgent):
         default=True,
         description="Use system prompt for the agent.",
     )
-    llm: Union[str, InstanceOf[LLM], Any] = Field(
+    llm: Union[str, InstanceOf[BaseLLM], Any] = Field(
         description="Language model that will run the agent.", default=None
     )
-    function_calling_llm: Optional[Union[str, InstanceOf[LLM], Any]] = Field(
+    function_calling_llm: Optional[Union[str, InstanceOf[BaseLLM], Any]] = Field(
         description="Language model that will run the agent.", default=None
     )
     system_template: Optional[str] = Field(
@@ -117,7 +117,7 @@ class Agent(BaseAgent):
         self.agent_ops_agent_name = self.role
 
         self.llm = create_llm(self.llm)
-        if self.function_calling_llm and not isinstance(self.function_calling_llm, LLM):
+        if self.function_calling_llm and not isinstance(self.function_calling_llm, BaseLLM):
             self.function_calling_llm = create_llm(self.function_calling_llm)
 
         if not self.agent_executor:
diff --git a/src/crewai/crew.py b/src/crewai/crew.py
index 9cecfed3a..2e3308177 100644
--- a/src/crewai/crew.py
+++ b/src/crewai/crew.py
@@ -26,7 +26,7 @@ from crewai.agents.cache import CacheHandler
 from crewai.crews.crew_output import CrewOutput
 from crewai.knowledge.knowledge import Knowledge
 from crewai.knowledge.source.base_knowledge_source import BaseKnowledgeSource
-from crewai.llm import LLM
+from crewai.llm import BaseLLM, LLM
 from crewai.memory.entity.entity_memory import EntityMemory
 from crewai.memory.long_term.long_term_memory import LongTermMemory
 from crewai.memory.short_term.short_term_memory import ShortTermMemory
@@ -150,7 +150,7 @@ class Crew(BaseModel):
         default=None,
         description="Metrics for the LLM usage during all tasks execution.",
     )
-    manager_llm: Optional[Any] = Field(
+    manager_llm: Optional[Union[str, InstanceOf[BaseLLM], Any]] = Field(
         description="Language model that will run the agent.", default=None
     )
     manager_agent: Optional[BaseAgent] = Field(
@@ -196,7 +196,7 @@ class Crew(BaseModel):
         default=False,
         description="Plan the crew execution and add the plan to the crew.",
     )
-    planning_llm: Optional[Any] = Field(
+    planning_llm: Optional[Union[str, InstanceOf[BaseLLM], Any]] = Field(
         default=None,
         description="Language model that will run the AgentPlanner if planning is True.",
     )
@@ -212,7 +212,7 @@ class Crew(BaseModel):
         default=None,
         description="Knowledge sources for the crew. Add knowledge sources to the knowledge object.",
     )
-    chat_llm: Optional[Any] = Field(
+    chat_llm: Optional[Union[str, InstanceOf[BaseLLM], Any]] = Field(
         default=None,
         description="LLM used to handle chatting with the crew.",
     )
@@ -1193,7 +1193,7 @@ class Crew(BaseModel):
     def test(
         self,
         n_iterations: int,
-        eval_llm: Union[str, InstanceOf[LLM]],
+        eval_llm: Union[str, InstanceOf[BaseLLM]],
         inputs: Optional[Dict[str, Any]] = None,
     ) -> None:
         """Test and evaluate the Crew with the given inputs for n iterations concurrently using concurrent.futures."""
diff --git a/src/crewai/llm.py b/src/crewai/llm.py
index 0c8a46214..a4b3e637e 100644
--- a/src/crewai/llm.py
+++ b/src/crewai/llm.py
@@ -4,6 +4,7 @@ import os
 import sys
 import threading
 import warnings
+from abc import ABC, abstractmethod
 from contextlib import contextmanager
 from typing import Any, Dict, List, Literal, Optional, Type, Union, cast
 
@@ -34,6 +35,78 @@ from crewai.utilities.exceptions.context_window_exceeding_exception import (
 load_dotenv()
 
 
+class BaseLLM(ABC):
+    """Abstract base class for LLM implementations.
+    
+    This class defines the interface that all LLM implementations must follow.
+    Users can extend this class to create custom LLM implementations that don't
+    rely on litellm's authentication mechanism.
+    """
+    
+    def __init__(self):
+        """Initialize the BaseLLM with default attributes.
+        
+        This constructor sets default values for attributes that are expected
+        by the CrewAgentExecutor and other components.
+        """
+        self.stop = []
+    
+    @abstractmethod
+    def call(
+        self,
+        messages: Union[str, List[Dict[str, str]]],
+        tools: Optional[List[dict]] = None,
+        callbacks: Optional[List[Any]] = None,
+        available_functions: Optional[Dict[str, Any]] = None,
+    ) -> Union[str, Any]:
+        """Call the LLM with the given messages.
+        
+        Args:
+            messages: Input messages for the LLM.
+                     Can be a string or list of message dictionaries.
+                     If string, it will be converted to a single user message.
+                     If list, each dict must have 'role' and 'content' keys.
+            tools: Optional list of tool schemas for function calling.
+                  Each tool should define its name, description, and parameters.
+            callbacks: Optional list of callback functions to be executed
+                      during and after the LLM call.
+            available_functions: Optional dict mapping function names to callables
+                               that can be invoked by the LLM.
+            
+        Returns:
+            Either a text response from the LLM (str) or
+            the result of a tool function call (Any).
+        """
+        pass
+        
+    @abstractmethod
+    def supports_function_calling(self) -> bool:
+        """Check if the LLM supports function calling.
+        
+        Returns:
+            True if the LLM supports function calling, False otherwise.
+        """
+        pass
+        
+    @abstractmethod
+    def supports_stop_words(self) -> bool:
+        """Check if the LLM supports stop words.
+        
+        Returns:
+            True if the LLM supports stop words, False otherwise.
+        """
+        pass
+        
+    @abstractmethod
+    def get_context_window_size(self) -> int:
+        """Get the context window size of the LLM.
+        
+        Returns:
+            The context window size as an integer.
+        """
+        pass
+
+
 class FilteredStream:
     def __init__(self, original_stream):
         self._original_stream = original_stream
@@ -126,7 +199,7 @@ def suppress_warnings():
             sys.stderr = old_stderr
 
 
-class LLM:
+class LLM(BaseLLM):
     def __init__(
         self,
         model: str,
diff --git a/src/crewai/utilities/llm_utils.py b/src/crewai/utilities/llm_utils.py
index 4d34d789c..3271e8bcb 100644
--- a/src/crewai/utilities/llm_utils.py
+++ b/src/crewai/utilities/llm_utils.py
@@ -2,28 +2,28 @@ import os
 from typing import Any, Dict, List, Optional, Union
 
 from crewai.cli.constants import DEFAULT_LLM_MODEL, ENV_VARS, LITELLM_PARAMS
-from crewai.llm import LLM
+from crewai.llm import BaseLLM, LLM
 
 
 def create_llm(
-    llm_value: Union[str, LLM, Any, None] = None,
-) -> Optional[LLM]:
+    llm_value: Union[str, BaseLLM, Any, None] = None,
+) -> Optional[BaseLLM]:
     """
     Creates or returns an LLM instance based on the given llm_value.
 
     Args:
-        llm_value (str | LLM | Any | None):
+        llm_value (str | BaseLLM | Any | None):
             - str: The model name (e.g., "gpt-4").
-            - LLM: Already instantiated LLM, returned as-is.
+            - BaseLLM: Already instantiated BaseLLM (including LLM), returned as-is.
             - Any: Attempt to extract known attributes like model_name, temperature, etc.
             - None: Use environment-based or fallback default model.
 
     Returns:
-        An LLM instance if successful, or None if something fails.
+        A BaseLLM instance if successful, or None if something fails.
     """
 
-    # 1) If llm_value is already an LLM object, return it directly
-    if isinstance(llm_value, LLM):
+    # 1) If llm_value is already a BaseLLM object, return it directly
+    if isinstance(llm_value, BaseLLM):
         return llm_value
 
     # 2) If llm_value is a string (model name)
diff --git a/tests/custom_llm_test.py b/tests/custom_llm_test.py
new file mode 100644
index 000000000..afedafbd5
--- /dev/null
+++ b/tests/custom_llm_test.py
@@ -0,0 +1,111 @@
+import pytest
+from typing import Any, Dict, List, Optional, Union
+
+from crewai.llm import BaseLLM
+from crewai.utilities.llm_utils import create_llm
+
+
+class CustomLLM(BaseLLM):
+    """Custom LLM implementation for testing."""
+    
+    def __init__(self, response: str = "Custom LLM response"):
+        self.response = response
+        self.calls = []
+        self.stop = []
+        
+    def call(
+        self,
+        messages: Union[str, List[Dict[str, str]]],
+        tools: Optional[List[dict]] = None,
+        callbacks: Optional[List[Any]] = None,
+        available_functions: Optional[Dict[str, Any]] = None,
+    ) -> Union[str, Any]:
+        """Record the call and return the predefined response."""
+        self.calls.append({
+            "messages": messages, 
+            "tools": tools,
+            "callbacks": callbacks,
+            "available_functions": available_functions
+        })
+        return self.response
+        
+    def supports_function_calling(self) -> bool:
+        """Return True to indicate that function calling is supported."""
+        return True
+        
+    def supports_stop_words(self) -> bool:
+        """Return True to indicate that stop words are supported."""
+        return True
+        
+    def get_context_window_size(self) -> int:
+        """Return a default context window size."""
+        return 8192
+
+
+def test_custom_llm_implementation():
+    """Test that a custom LLM implementation works with create_llm."""
+    custom_llm = CustomLLM(response="The answer is 42")
+    
+    # Test that create_llm returns the custom LLM instance directly
+    result_llm = create_llm(custom_llm)
+    
+    assert result_llm is custom_llm
+    
+    # Test calling the custom LLM
+    response = result_llm.call("What is the answer to life, the universe, and everything?")
+    
+    # Verify that the custom LLM was called
+    assert len(custom_llm.calls) > 0
+    # Verify that the response from the custom LLM was used
+    assert response == "The answer is 42"
+
+
+class JWTAuthLLM(BaseLLM):
+    def __init__(self, jwt_token: str):
+        self.jwt_token = jwt_token
+        self.calls = []
+        self.stop = []
+        
+    def call(
+        self,
+        messages: Union[str, List[Dict[str, str]]],
+        tools: Optional[List[dict]] = None,
+        callbacks: Optional[List[Any]] = None,
+        available_functions: Optional[Dict[str, Any]] = None,
+    ) -> Union[str, Any]:
+        self.calls.append({
+            "messages": messages, 
+            "tools": tools,
+            "callbacks": callbacks,
+            "available_functions": available_functions
+        })
+        # In a real implementation, this would use the JWT token to authenticate
+        # with an external service
+        return "Response from JWT-authenticated LLM"
+        
+    def supports_function_calling(self) -> bool:
+        return True
+        
+    def supports_stop_words(self) -> bool:
+        return True
+        
+    def get_context_window_size(self) -> int:
+        return 8192
+
+
+def test_custom_llm_with_jwt_auth():
+    """Test a custom LLM implementation with JWT authentication."""
+    jwt_llm = JWTAuthLLM(jwt_token="example.jwt.token")
+    
+    # Test that create_llm returns the JWT-authenticated LLM instance directly
+    result_llm = create_llm(jwt_llm)
+    
+    assert result_llm is jwt_llm
+    
+    # Test calling the JWT-authenticated LLM
+    response = result_llm.call("Test message")
+    
+    # Verify that the JWT-authenticated LLM was called
+    assert len(jwt_llm.calls) > 0
+    # Verify that the response from the JWT-authenticated LLM was used
+    assert response == "Response from JWT-authenticated LLM"