diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
index 23cc6d8faae2da..7717e67a513649 100644
--- a/Lib/_collections_abc.py
+++ b/Lib/_collections_abc.py
@@ -925,7 +925,7 @@ def __setitem__(self, key, value):
     def __delitem__(self, key):
         raise KeyError
 
-    __marker = object()
+    __marker = sentinel("__marker")
 
     def pop(self, key, default=__marker):
         '''D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index b6d68f2372850a..d388ca46013606 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -2447,7 +2447,7 @@ class timezone(tzinfo):
     __slots__ = '_offset', '_name'
 
     # Sentinel value to disallow None
-    _Omitted = object()
+    _Omitted = sentinel("_Omitted")
     def __new__(cls, offset, name=_Omitted):
         if not isinstance(offset, timedelta):
             raise TypeError("offset must be a timedelta")
diff --git a/Lib/configparser.py b/Lib/configparser.py
index a53ac87276445a..af2d872f487e0f 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -392,7 +392,7 @@ def __init__(self, msg=''):
 # Used in parser getters to indicate the default behaviour when a specific
 # option is not found it to raise an exception. Created to enable `None` as
 # a valid fallback value.
-_UNSET = object()
+_UNSET = sentinel("_UNSET")
 
 
 class Interpolation:
diff --git a/Lib/functools.py b/Lib/functools.py
index 409b2c50478c40..5a65addce24127 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -1137,7 +1137,7 @@ def register(self):
 ### cached_property() - property result cached as instance attribute
 ################################################################################
 
-_NOT_FOUND = object()
+_NOT_FOUND = sentinel("_NOT_FOUND")
 
 class cached_property:
     def __init__(self, func):
diff --git a/Lib/inspect.py b/Lib/inspect.py
index a96b3dc954ef0c..22fb2ebfb074fb 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1694,7 +1694,7 @@ def trace(context=1):
 
 # ------------------------------------------------ static version of getattr
 
-_sentinel = object()
+_sentinel = sentinel("_sentinel")
 _static_getmro = type.__dict__['__mro__'].__get__
 _get_dunder_dict_of_class = type.__dict__["__dict__"].__get__
 
diff --git a/Lib/sched.py b/Lib/sched.py
index fb20639d459967..56555d025f7201 100644
--- a/Lib/sched.py
+++ b/Lib/sched.py
@@ -46,7 +46,7 @@
 Event.kwargs.__doc__ = ('''kwargs is a dictionary holding the keyword
 arguments for the action.''')
 
-_sentinel = object()
+_sentinel = sentinel("_sentinel")
 
 class scheduler:
 
diff --git a/Misc/NEWS.d/next/Library/2026-04-27-19-47-24.gh-issue-149083.xa_4JR.rst b/Misc/NEWS.d/next/Library/2026-04-27-19-47-24.gh-issue-149083.xa_4JR.rst
new file mode 100644
index 00000000000000..8d5d2aa4abfbc9
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-04-27-19-47-24.gh-issue-149083.xa_4JR.rst
@@ -0,0 +1,2 @@
+Various private sentinels in the standard library are now instances of
+:class:`sentinel`.