diff --git a/mesa/agent.py b/mesa/agent.py
index 5504e1be06b..044b40acecf 100644
--- a/mesa/agent.py
+++ b/mesa/agent.py
@@ -155,7 +155,6 @@ def select(
         at_most: int | float = float("inf"),
         inplace: bool = False,
         agent_type: type[Agent] | None = None,
-        n: int | None = None,
     ) -> AgentSet:
         """Select a subset of agents from the AgentSet based on a filter function and/or quantity limit.
 
@@ -167,7 +166,6 @@ def select(
               - If a float between 0 and 1, at most that fraction of original the agents are selected.
             inplace (bool, optional): If True, modifies the current AgentSet; otherwise, returns a new AgentSet. Defaults to False.
             agent_type (type[Agent], optional): The class type of the agents to select. Defaults to None, meaning no type filtering is applied.
-            n (int): deprecated, use at_most instead
 
         Returns:
             AgentSet: A new AgentSet containing the selected agents, unless inplace is True, in which case the current AgentSet is updated.
@@ -176,14 +174,6 @@ def select(
             - at_most just return the first n or fraction of agents. To take a random sample, shuffle() beforehand.
             - at_most is an upper limit. When specifying other criteria, the number of agents returned can be smaller.
         """
-        if n is not None:
-            warnings.warn(
-                "The parameter 'n' is deprecated and will be removed in Mesa 3.1. Use 'at_most' instead.",
-                DeprecationWarning,
-                stacklevel=2,
-            )
-            at_most = n
-
         inf = float("inf")
         if filter_func is None and agent_type is None and at_most == inf:
             return self if inplace else copy.copy(self)
@@ -281,21 +271,6 @@ def do(self, method: str | Callable, *args, **kwargs) -> AgentSet:
         Returns:
             AgentSet | list[Any]: The results of the callable calls if return_results is True, otherwise the AgentSet itself.
         """
-        try:
-            return_results = kwargs.pop("return_results")
-        except KeyError:
-            return_results = False
-        else:
-            warnings.warn(
-                "Using return_results is deprecated and will be removed in Mesa 3.1."
-                "Use AgenSet.do in case of return_results=False, and AgentSet.map in case of return_results=True",
-                DeprecationWarning,
-                stacklevel=2,
-            )
-
-        if return_results:
-            return self.map(method, *args, **kwargs)
-
         # we iterate over the actual weakref keys and check if weakref is alive before calling the method
         if isinstance(method, str):
             for agentref in self._agents.keyrefs():
diff --git a/mesa/model.py b/mesa/model.py
index 57af030e4b4..f89be92e7f6 100644
--- a/mesa/model.py
+++ b/mesa/model.py
@@ -18,7 +18,6 @@
 import numpy as np
 
 from mesa.agent import Agent, AgentSet
-from mesa.datacollection import DataCollector
 
 SeedLike = int | np.integer | Sequence[int] | np.random.SeedSequence
 RNGLike = np.random.Generator | np.random.BitGenerator
@@ -112,14 +111,6 @@ def _wrapped_step(self, *args: Any, **kwargs: Any) -> None:
         # Call the original user-defined step method
         self._user_step(*args, **kwargs)
 
-    def next_id(self) -> int:  # noqa: D102
-        warnings.warn(
-            "using model.next_id() is deprecated and will be removed in Mesa 3.1. Agents track their unique ID automatically",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        return 0
-
     @property
     def agents(self) -> AgentSet:
         """Provides an AgentSet of all agents in the model, combining agents from all types."""
@@ -143,16 +134,6 @@ def agents_by_type(self) -> dict[type[Agent], AgentSet]:
         """A dictionary where the keys are agent types and the values are the corresponding AgentSets."""
         return self._agents_by_type
 
-    def get_agents_of_type(self, agenttype: type[Agent]) -> AgentSet:
-        """Deprecated: Retrieves an AgentSet containing all agents of the specified type."""
-        warnings.warn(
-            f"Model.get_agents_of_type() is deprecated and will be removed in Mesa 3.1."
-            f"Please replace get_agents_of_type({agenttype}) with the property agents_by_type[{agenttype}].",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        return self.agents_by_type[agenttype]
-
     def _setup_agent_registration(self):
         """Helper method to initialize the agent registration datastructures."""
         self._agents = {}  # the hard references to all agents in the model
@@ -245,38 +226,6 @@ def reset_rng(self, rng: RNGLike | SeedLike | None = None) -> None:
         self.rng = np.random.default_rng(rng)
         self._rng = self.rng.bit_generator.state
 
-    def initialize_data_collector(
-        self,
-        model_reporters=None,
-        agent_reporters=None,
-        agenttype_reporters=None,
-        tables=None,
-    ) -> None:
-        """Initialize the data collector for the model.
-
-        Args:
-            model_reporters: model reporters to collect
-            agent_reporters: agent reporters to collect
-            agenttype_reporters: agent type reporters to collect
-            tables: tables to collect
-
-        """
-        warnings.warn(
-            "initialize_data_collector() is deprecated and will be removed in Mesa 3.1. Please use the DataCollector class directly. "
-            "by using `self.datacollector = DataCollector(...)`.",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-
-        self.datacollector = DataCollector(
-            model_reporters=model_reporters,
-            agent_reporters=agent_reporters,
-            agenttype_reporters=agenttype_reporters,
-            tables=tables,
-        )
-        # Collect data for the first time during initialization.
-        self.datacollector.collect(self)
-
     def remove_all_agents(self):
         """Remove all agents from the model.