diff --git a/README.md b/README.md
index e5e4a51c..43c107ea 100644
--- a/README.md
+++ b/README.md
@@ -906,6 +906,11 @@ Some notes about activity definition:
   "Activity Concurrency and Executors" section later for more details.
 * Technically an activity definition can be created manually via `Temporalio::Activity::Definition::Info.new` that
   accepts a proc or a block, but the class form is recommended.
+* `activity_dynamic` can be used to mark an activity dynamic. Dynamic activities do not have names and handle any
+  activity that is not otherwise registered. A worker can only have one dynamic activity.
+* `workflow_raw_args` can be used to have activity arguments delivered to `execute` as
+  `Temporalio::Converters::RawValue`s. These are wrappers for the raw payloads that have not been converted to types
+  (but they have been decoded by the codec if present). They can be converted with `payload_converter` on the context.
 
 #### Activity Context
 
diff --git a/temporalio/lib/temporalio/activity/definition.rb b/temporalio/lib/temporalio/activity/definition.rb
index c107ca87..58d8641a 100644
--- a/temporalio/lib/temporalio/activity/definition.rb
+++ b/temporalio/lib/temporalio/activity/definition.rb
@@ -49,20 +49,47 @@ def activity_executor(executor_name)
         # @param cancel_raise [Boolean] Whether to raise.
         def activity_cancel_raise(cancel_raise)
           unless cancel_raise.is_a?(TrueClass) || cancel_raise.is_a?(FalseClass)
-            raise ArgumentError,
-                  'Must be a boolean'
+            raise ArgumentError, 'Must be a boolean'
           end
 
           @activity_cancel_raise = cancel_raise
         end
+
+        # Set an activity as dynamic. Dynamic activities do not have names and handle any activity that is not otherwise
+        # registered. A worker can only have one dynamic activity. It is often useful to use {activity_raw_args} with
+        # this.
+        #
+        # @param value [Boolean] Whether the activity is dynamic.
+        def activity_dynamic(value = true) # rubocop:disable Style/OptionalBooleanParameter
+          raise ArgumentError, 'Must be a boolean' unless value.is_a?(TrueClass) || value.is_a?(FalseClass)
+
+          @activity_dynamic = value
+        end
+
+        # Have activity arguments delivered to `execute` as {Converters::RawValue}s. These are wrappers for the raw
+        # payloads that have not been converted to types (but they have been decoded by the codec if present). They can
+        # be converted with {Context#payload_converter}.
+        #
+        # @param value [Boolean] Whether the activity accepts raw arguments.
+        def activity_raw_args(value = true) # rubocop:disable Style/OptionalBooleanParameter
+          raise ArgumentError, 'Must be a boolean' unless value.is_a?(TrueClass) || value.is_a?(FalseClass)
+
+          @activity_raw_args = value
+        end
       end
 
       # @!visibility private
       def self._activity_definition_details
+        activity_name = @activity_name
+        raise 'Cannot have activity name specified for dynamic activity' if activity_name && @activity_dynamic
+
+        # Default to unqualified class name if not dynamic
+        activity_name ||= name.to_s.split('::').last unless @activity_dynamic
         {
-          activity_name: @activity_name || name.to_s.split('::').last,
+          activity_name:,
           activity_executor: @activity_executor || :default,
-          activity_cancel_raise: @activity_cancel_raise.nil? ? true : @activity_cancel_raise
+          activity_cancel_raise: @activity_cancel_raise.nil? ? true : @activity_cancel_raise,
+          activity_raw_args: @activity_raw_args.nil? ? false : @activity_raw_args
         }
       end
 
@@ -75,7 +102,7 @@ def execute(*args)
       # Definition info of an activity. Activities are usually classes/instances that extend {Definition}, but
       # definitions can also be manually created with a block via {initialize} here.
       class Info
-        # @return [String, Symbol] Name of the activity.
+        # @return [String, Symbol, nil] Name of the activity, or nil if the activity is dynamic.
         attr_reader :name
 
         # @return [Proc] Proc for the activity.
@@ -87,6 +114,9 @@ class Info
         # @return [Boolean] Whether to raise in thread/fiber on cancellation. Default is `true`.
         attr_reader :cancel_raise
 
+        # @return [Boolean] Whether to use {Converters::RawValue}s as arguments.
+        attr_reader :raw_args
+
         # Obtain definition info representing the given activity, which can be a class, instance, or definition info.
         #
         # @param activity [Definition, Class<Definition>, Info] Activity to get info for.
@@ -105,14 +135,16 @@ def self.from_activity(activity)
             new(
               name: details[:activity_name],
               executor: details[:activity_executor],
-              cancel_raise: details[:activity_cancel_raise]
+              cancel_raise: details[:activity_cancel_raise],
+              raw_args: details[:activity_raw_args]
             ) { |*args| activity.new.execute(*args) } # Instantiate and call
           when Definition
             details = activity.class._activity_definition_details
             new(
               name: details[:activity_name],
               executor: details[:activity_executor],
-              cancel_raise: details[:activity_cancel_raise]
+              cancel_raise: details[:activity_cancel_raise],
+              raw_args: details[:activity_raw_args]
             ) { |*args| activity.execute(*args) } # Just and call
           when Info
             activity
@@ -123,17 +155,19 @@ def self.from_activity(activity)
 
         # Manually create activity definition info. Most users will use an instance/class of {Definition}.
         #
-        # @param name [String, Symbol] Name of the activity.
+        # @param name [String, Symbol, nil] Name of the activity or nil for dynamic activity.
         # @param executor [Symbol] Name of the executor.
         # @param cancel_raise [Boolean] Whether to raise in thread/fiber on cancellation.
+        # @param raw_args [Boolean] Whether to use {Converters::RawValue}s as arguments.
         # @yield Use this block as the activity.
-        def initialize(name:, executor: :default, cancel_raise: true, &block)
+        def initialize(name:, executor: :default, cancel_raise: true, raw_args: false, &block)
           @name = name
           raise ArgumentError, 'Must give block' unless block_given?
 
           @proc = block
           @executor = executor
           @cancel_raise = cancel_raise
+          @raw_args = raw_args
         end
       end
     end
diff --git a/temporalio/lib/temporalio/internal/worker/activity_worker.rb b/temporalio/lib/temporalio/internal/worker/activity_worker.rb
index b727c48b..46cd0f1f 100644
--- a/temporalio/lib/temporalio/internal/worker/activity_worker.rb
+++ b/temporalio/lib/temporalio/internal/worker/activity_worker.rb
@@ -3,6 +3,7 @@
 require 'temporalio/activity'
 require 'temporalio/activity/definition'
 require 'temporalio/cancellation'
+require 'temporalio/converters/raw_value'
 require 'temporalio/internal/bridge/api'
 require 'temporalio/internal/proto_utils'
 require 'temporalio/scoped_logger'
@@ -29,12 +30,13 @@ def initialize(worker:, bridge_worker:)
             Activity::Context.current_or_nil&._scoped_logger_info
           }
 
-          # Build up activity hash by name, failing if any fail validation
+          # Build up activity hash by name (can be nil for dynamic), failing if any fail validation
           @activities = worker.options.activities.each_with_object({}) do |act, hash|
             # Class means create each time, instance means just call, definition
             # does nothing special
             defn = Activity::Definition::Info.from_activity(act)
             # Confirm name not in use
+            raise ArgumentError, 'Only one dynamic activity allowed' if !defn.name && hash.key?(defn.name)
             raise ArgumentError, "Multiple activities named #{defn.name}" if hash.key?(defn.name)
 
             # Confirm executor is a known executor and let it initialize
@@ -91,8 +93,8 @@ def handle_task(task)
         def handle_start_task(task_token, start)
           set_running_activity(task_token, nil)
 
-          # Find activity definition
-          defn = @activities[start.activity_type]
+          # Find activity definition, falling back to dynamic if present
+          defn = @activities[start.activity_type] || @activities[nil]
           if defn.nil?
             raise Error::ApplicationError.new(
               "Activity #{start.activity_type} for workflow #{start.workflow_execution.workflow_id} " \
@@ -185,10 +187,15 @@ def execute_activity(task_token, defn, start)
           # Build input
           input = Temporalio::Worker::Interceptor::Activity::ExecuteInput.new(
             proc: defn.proc,
-            args: ProtoUtils.convert_from_payload_array(
-              @worker.options.client.data_converter,
-              start.input.to_ary
-            ),
+            # If the activity wants raw_args, we only decode we don't convert
+            args: if defn.raw_args
+                    payloads = start.input.to_ary
+                    codec = @worker.options.client.data_converter.payload_codec
+                    payloads = codec.decode(payloads) if codec
+                    payloads.map { |p| Temporalio::Converters::RawValue.new(p) }
+                  else
+                    ProtoUtils.convert_from_payload_array(@worker.options.client.data_converter, start.input.to_ary)
+                  end,
             headers: ProtoUtils.headers_from_proto_map(start.header_fields, @worker.options.client.data_converter) || {}
           )
 
diff --git a/temporalio/lib/temporalio/internal/worker/workflow_instance/outbound_implementation.rb b/temporalio/lib/temporalio/internal/worker/workflow_instance/outbound_implementation.rb
index 5cf46c25..6dc3ee50 100644
--- a/temporalio/lib/temporalio/internal/worker/workflow_instance/outbound_implementation.rb
+++ b/temporalio/lib/temporalio/internal/worker/workflow_instance/outbound_implementation.rb
@@ -64,6 +64,8 @@ def execute_activity(input)
                             else
                               raise ArgumentError, 'Activity must be a definition class, or a symbol/string'
                             end
+            raise 'Cannot invoke dynamic activities' unless activity_type
+
             execute_activity_with_local_backoffs(local: false, cancellation: input.cancellation) do
               seq = (@activity_counter += 1)
               @instance.add_command(
@@ -102,6 +104,8 @@ def execute_local_activity(input)
                             else
                               raise ArgumentError, 'Activity must be a definition class, or a symbol/string'
                             end
+            raise 'Cannot invoke dynamic activities' unless activity_type
+
             execute_activity_with_local_backoffs(local: true, cancellation: input.cancellation) do |do_backoff|
               seq = (@activity_counter += 1)
               @instance.add_command(
diff --git a/temporalio/lib/temporalio/workflow/definition.rb b/temporalio/lib/temporalio/workflow/definition.rb
index d926395a..7395a9b1 100644
--- a/temporalio/lib/temporalio/workflow/definition.rb
+++ b/temporalio/lib/temporalio/workflow/definition.rb
@@ -38,8 +38,8 @@ def workflow_dynamic(value = true) # rubocop:disable Style/OptionalBooleanParame
         end
 
         # Have workflow arguments delivered to `execute` (and `initialize` if {workflow_init} in use) as
-        # {Converters::RawValue}s. These are wrappers for the raw payloads that have not been decoded. They can be
-        # decoded with {Workflow.payload_converter}.
+        # {Converters::RawValue}s. These are wrappers for the raw payloads that have not been converted to types (but
+        # they have been decoded by the codec if present). They can be converted with {Workflow.payload_converter}.
         #
         # @param value [Boolean] Whether the workflow accepts raw arguments.
         def workflow_raw_args(value = true) # rubocop:disable Style/OptionalBooleanParameter
diff --git a/temporalio/sig/temporalio/activity/definition.rbs b/temporalio/sig/temporalio/activity/definition.rbs
index e3bdd324..b838fb7b 100644
--- a/temporalio/sig/temporalio/activity/definition.rbs
+++ b/temporalio/sig/temporalio/activity/definition.rbs
@@ -4,27 +4,32 @@ module Temporalio
       def self.activity_name: (String | Symbol name) -> void
       def self.activity_executor: (Symbol executor_name) -> void
       def self.activity_cancel_raise: (bool cancel_raise) -> void
+      def self.activity_dynamic: (?bool value) -> void
+      def self.activity_raw_args: (?bool value) -> void
   
       def self._activity_definition_details: -> {
-        activity_name: String | Symbol,
+        activity_name: String | Symbol | nil,
         activity_executor: Symbol,
-        activity_cancel_raise: bool
+        activity_cancel_raise: bool,
+        activity_raw_args: bool
       }
   
       def execute: (*untyped) -> untyped
 
       class Info
-        attr_reader name: String | Symbol
+        attr_reader name: String | Symbol | nil
         attr_reader proc: Proc
         attr_reader executor: Symbol
         attr_reader cancel_raise: bool
+        attr_reader raw_args: bool
 
         def self.from_activity: (Definition | singleton(Definition) | Info activity) -> Info
 
         def initialize: (
-          name: String | Symbol,
+          name: String | Symbol | nil,
           ?executor: Symbol,
-          ?cancel_raise: bool
+          ?cancel_raise: bool,
+          ?raw_args: bool
         ) { (?) -> untyped } -> void
       end
     end
diff --git a/temporalio/test/worker_activity_test.rb b/temporalio/test/worker_activity_test.rb
index 2558e228..5ed29788 100644
--- a/temporalio/test/worker_activity_test.rb
+++ b/temporalio/test/worker_activity_test.rb
@@ -822,6 +822,41 @@ def test_interceptor_from_client
     assert_equal ['heartbeat-val'], interceptor.calls[2][1].details
   end
 
+  class DynamicActivity < Temporalio::Activity::Definition
+    activity_dynamic
+
+    def execute(*args)
+      "Activity #{Temporalio::Activity::Context.current.info.activity_type} called with #{args}"
+    end
+  end
+
+  def test_dynamic_activity
+    assert_equal 'Activity does-not-exist called with ["arg1", 123]',
+                 execute_activity(DynamicActivity, 'arg1', 123, override_name: 'does-not-exist')
+  end
+
+  class DynamicActivityRawArgs < Temporalio::Activity::Definition
+    activity_dynamic
+    activity_raw_args
+
+    def execute(*args)
+      metadata_encodings, decoded_args = args.map do |arg|
+        raise 'Bad type' unless arg.is_a?(Temporalio::Converters::RawValue)
+
+        [arg.payload.metadata['encoding'],
+         Temporalio::Activity::Context.current.payload_converter.from_payload(arg.payload)]
+      end.transpose
+      "Activity #{Temporalio::Activity::Context.current.info.activity_type} called with " \
+        "#{decoded_args} that have encodings #{metadata_encodings}"
+    end
+  end
+
+  def test_dynamic_activity_raw_args
+    assert_equal 'Activity does-not-exist called with ' \
+                 '["arg1", nil, 123] that have encodings ["json/plain", "binary/null", "json/plain"]',
+                 execute_activity(DynamicActivityRawArgs, 'arg1', nil, 123, override_name: 'does-not-exist')
+  end
+
   # steep:ignore
   def execute_activity(
     activity,