diff --git a/Doc/faq/library.rst b/Doc/faq/library.rst
index 97058b5806a35c..4d27abd4351ec0 100644
--- a/Doc/faq/library.rst
+++ b/Doc/faq/library.rst
@@ -319,11 +319,11 @@ Here's a trivial example::
            try:
                arg = q.get(block=False)
            except queue.Empty:
-               print('Worker', threading.currentThread(), end=' ')
+               print('Worker', threading.current_thread(), end=' ')
                print('queue empty')
                break
            else:
-               print('Worker', threading.currentThread(), end=' ')
+               print('Worker', threading.current_thread(), end=' ')
                print('running with argument', arg)
                time.sleep(0.5)
 
diff --git a/Doc/library/idle.rst b/Doc/library/idle.rst
index 6ef15653eacb55..3c302115b5f408 100644
--- a/Doc/library/idle.rst
+++ b/Doc/library/idle.rst
@@ -732,7 +732,7 @@ intended to be the same as executing the same code by the default method,
 directly with Python in a text-mode system console or terminal window.
 However, the different interface and operation occasionally affect
 visible results.  For instance, ``sys.modules`` starts with more entries,
-and ``threading.activeCount()`` returns 2 instead of 1.
+and ``threading.active_count()`` returns 2 instead of 1.
 
 By default, IDLE runs user code in a separate OS process rather than in
 the user interface process that runs the shell and editor.  In the execution
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index bb982f2edcf1b2..16f23c3a0c3548 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -16,9 +16,9 @@ level :mod:`_thread` module.  See also the :mod:`queue` module.
 
 .. note::
 
-   While they are not listed below, the ``camelCase`` names used for some
-   methods and functions in this module in the Python 2.x series are still
-   supported by this module.
+   In the Python 2.x series, this module contained ``camelCase`` names
+   for some methods and functions. These are deprecated as of Python 3.10,
+   but they are still supported for compatibility with Python 2.5 and lower.
 
 
 .. impl-detail::
@@ -42,6 +42,8 @@ This module defines the following functions:
    Return the number of :class:`Thread` objects currently alive.  The returned
    count is equal to the length of the list returned by :func:`.enumerate`.
 
+   The function ``activeCount`` is a deprecated alias for this function.
+
 
 .. function:: current_thread()
 
@@ -50,6 +52,8 @@ This module defines the following functions:
    :mod:`threading` module, a dummy thread object with limited functionality is
    returned.
 
+   The function ``currentThread`` is a deprecated alias for this function.
+
 
 .. function:: excepthook(args, /)
 
@@ -381,9 +385,11 @@ since it is impossible to detect the termination of alien threads.
    .. method:: getName()
                setName()
 
-      Old getter/setter API for :attr:`~Thread.name`; use it directly as a
+      Deprecated getter/setter API for :attr:`~Thread.name`; use it directly as a
       property instead.
 
+      .. deprecated:: 3.10
+
    .. attribute:: ident
 
       The 'thread identifier' of this thread or ``None`` if the thread has not
@@ -433,9 +439,11 @@ since it is impossible to detect the termination of alien threads.
    .. method:: isDaemon()
                setDaemon()
 
-      Old getter/setter API for :attr:`~Thread.daemon`; use it directly as a
+      Deprecated getter/setter API for :attr:`~Thread.daemon`; use it directly as a
       property instead.
 
+      .. deprecated:: 3.10
+
 
 .. _lock-objects:
 
@@ -771,6 +779,8 @@ item to the buffer only needs to wake up one consumer thread.
       calling thread has not acquired the lock when this method is called, a
       :exc:`RuntimeError` is raised.
 
+      The method ``notifyAll`` is a deprecated alias for this method.
+
 
 .. _semaphore-objects:
 
@@ -908,6 +918,8 @@ method.  The :meth:`~Event.wait` method blocks until the flag is true.
 
       Return ``True`` if and only if the internal flag is true.
 
+      The method ``isSet`` is a deprecated alias for this method.
+
    .. method:: set()
 
       Set the internal flag to true. All threads waiting for it to become true
diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index 9f6b7a469ca492..85f229cd787173 100644
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -1129,6 +1129,27 @@ Deprecated
   ``cache=shared`` query parameter.
   (Contributed by Erlend E. Aasland in :issue:`24464`.)
 
+* The following ``threading`` methods are now deprecated:
+
+  * ``threading.currentThread`` => :func:`threading.current_thread`
+
+  * ``threading.activeCount`` => :func:`threading.active_count`
+
+  * ``threading.Condition.notifyAll`` =>
+    :meth:`threading.Condition.notify_all`
+
+  * ``threading.Event.isSet`` => :meth:`threading.Event.is_set`
+
+  * ``threading.Thread.setName`` => :attr:`threading.Thread.name`
+
+  * ``threading.thread.getName`` => :attr:`threading.Thread.name`
+
+  * ``threading.Thread.isDaemon`` => :attr:`threading.Thread.daemon`
+
+  * ``threading.Thread.setDaemon`` => :attr:`threading.Thread.daemon`
+
+  (Contributed by Jelle Zijlstra in :issue:`21574`.)
+
 
 Removed
 =======
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index 933935ba2ce2c8..49a4af8365afce 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -154,9 +154,9 @@ def test_various_ops(self):
 
     def test_ident_of_no_threading_threads(self):
         # The ident still must work for the main thread and dummy threads.
-        self.assertIsNotNone(threading.currentThread().ident)
+        self.assertIsNotNone(threading.current_thread().ident)
         def f():
-            ident.append(threading.currentThread().ident)
+            ident.append(threading.current_thread().ident)
             done.set()
         done = threading.Event()
         ident = []
@@ -447,13 +447,32 @@ def test_old_threading_api(self):
         # Just a quick sanity check to make sure the old method names are
         # still present
         t = threading.Thread()
-        t.isDaemon()
-        t.setDaemon(True)
-        t.getName()
-        t.setName("name")
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'get the daemon attribute'):
+            t.isDaemon()
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'set the daemon attribute'):
+            t.setDaemon(True)
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'get the name attribute'):
+            t.getName()
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'set the name attribute'):
+            t.setName("name")
+
         e = threading.Event()
-        e.isSet()
-        threading.activeCount()
+        with self.assertWarnsRegex(DeprecationWarning, 'use is_set()'):
+            e.isSet()
+
+        cond = threading.Condition()
+        cond.acquire()
+        with self.assertWarnsRegex(DeprecationWarning, 'use notify_all()'):
+            cond.notifyAll()
+
+        with self.assertWarnsRegex(DeprecationWarning, 'use active_count()'):
+            threading.activeCount()
+        with self.assertWarnsRegex(DeprecationWarning, 'use current_thread()'):
+            threading.currentThread()
 
     def test_repr_daemon(self):
         t = threading.Thread()
diff --git a/Lib/threading.py b/Lib/threading.py
index ff2624a3e1e49e..4dcf84715c439d 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -388,7 +388,16 @@ def notify_all(self):
         """
         self.notify(len(self._waiters))
 
-    notifyAll = notify_all
+    def notifyAll(self):
+        """Wake up all threads waiting on this condition.
+
+        This method is deprecated, use notify_all() instead.
+
+        """
+        import warnings
+        warnings.warn('notifyAll() is deprecated, use notify_all() instead',
+                      DeprecationWarning, stacklevel=2)
+        self.notify_all()
 
 
 class Semaphore:
@@ -538,7 +547,16 @@ def is_set(self):
         """Return true if and only if the internal flag is true."""
         return self._flag
 
-    isSet = is_set
+    def isSet(self):
+        """Return true if and only if the internal flag is true.
+
+        This method is deprecated, use notify_all() instead.
+
+        """
+        import warnings
+        warnings.warn('isSet() is deprecated, use is_set() instead',
+                      DeprecationWarning, stacklevel=2)
+        return self.is_set()
 
     def set(self):
         """Set the internal flag to true.
@@ -1146,15 +1164,47 @@ def daemon(self, daemonic):
         self._daemonic = daemonic
 
     def isDaemon(self):
+        """Return whether this thread is a daemon.
+
+        This method is deprecated, use the daemon attribute instead.
+
+        """
+        import warnings
+        warnings.warn('isDaemon() is deprecated, get the daemon attribute instead',
+                      DeprecationWarning, stacklevel=2)
         return self.daemon
 
     def setDaemon(self, daemonic):
+        """Set whether this thread is a daemon.
+
+        This method is deprecated, use the .daemon property instead.
+
+        """
+        import warnings
+        warnings.warn('setDaemon() is deprecated, set the daemon attribute instead',
+                      DeprecationWarning, stacklevel=2)
         self.daemon = daemonic
 
     def getName(self):
+        """Return a string used for identification purposes only.
+
+        This method is deprecated, use the name attribute instead.
+
+        """
+        import warnings
+        warnings.warn('getName() is deprecated, get the name attribute instead',
+                      DeprecationWarning, stacklevel=2)
         return self.name
 
     def setName(self, name):
+        """Set the name string for this thread.
+
+        This method is deprecated, use the name attribute instead.
+
+        """
+        import warnings
+        warnings.warn('setName() is deprecated, set the name attribute instead',
+                      DeprecationWarning, stacklevel=2)
         self.name = name
 
 
@@ -1349,7 +1399,16 @@ def current_thread():
     except KeyError:
         return _DummyThread()
 
-currentThread = current_thread
+def currentThread():
+    """Return the current Thread object, corresponding to the caller's thread of control.
+
+    This function is deprecated, use current_thread() instead.
+
+    """
+    import warnings
+    warnings.warn('currentThread() is deprecated, use current_thread() instead',
+                  DeprecationWarning, stacklevel=2)
+    return current_thread()
 
 def active_count():
     """Return the number of Thread objects currently alive.
@@ -1361,7 +1420,16 @@ def active_count():
     with _active_limbo_lock:
         return len(_active) + len(_limbo)
 
-activeCount = active_count
+def activeCount():
+    """Return the number of Thread objects currently alive.
+
+    This function is deprecated, use active_count() instead.
+
+    """
+    import warnings
+    warnings.warn('activeCount() is deprecated, use active_count() instead',
+                  DeprecationWarning, stacklevel=2)
+    return active_count()
 
 def _enumerate():
     # Same as enumerate(), but without the lock. Internal use only.
diff --git a/Misc/NEWS.d/next/Library/2021-04-03-18-03-44.bpo-43723.uBhBZS.rst b/Misc/NEWS.d/next/Library/2021-04-03-18-03-44.bpo-43723.uBhBZS.rst
new file mode 100644
index 00000000000000..27cf7aa716273c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-04-03-18-03-44.bpo-43723.uBhBZS.rst
@@ -0,0 +1,19 @@
+The following ``threading`` methods are now deprecated and should be replaced:
+
+- ``currentThread`` => :func:`threading.current_thread`
+
+- ``activeCount`` => :func:`threading.active_count`
+
+- ``Condition.notifyAll`` => :meth:`threading.Condition.notify_all`
+
+- ``Event.isSet`` => :meth:`threading.Event.is_set`
+
+- ``Thread.setName`` => :attr:`threading.Thread.name`
+
+- ``thread.getName`` => :attr:`threading.Thread.name`
+
+- ``Thread.isDaemon`` => :attr:`threading.Thread.daemon`
+
+- ``Thread.setDaemon`` => :attr:`threading.Thread.daemon`
+
+Patch by Jelle Zijlstra.