diff --git a/Doc/library/random.rst b/Doc/library/random.rst
index ad4a1ce7c31275..de553627f1b81e 100644
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -224,7 +224,7 @@ Functions for sequences
       The optional parameter *random*.
 
 
-.. function:: sample(population, k, *, counts=None)
+.. function:: sample(population, k=None, *, counts=None)
 
    Return a *k* length list of unique elements chosen from the population
    sequence.  Used for random sampling without replacement.
@@ -238,6 +238,10 @@ Functions for sequences
    Members of the population need not be :term:`hashable` or unique.  If the population
    contains repeats, then each occurrence is a possible selection in the sample.
 
+   The number of elements to sample is specified through the *k* parameter.  If
+   omitted, it defaults to ``len(population)``, and the function returns a shuffled
+   copy of the sequence.
+
    Repeated elements can be specified one at a time or with the optional
    keyword-only *counts* parameter.  For example, ``sample(['red', 'blue'],
    counts=[4, 2], k=5)`` is equivalent to ``sample(['red', 'red', 'red', 'red',
@@ -258,6 +262,8 @@ Functions for sequences
       The *population* must be a sequence.  Automatic conversion of sets
       to lists is no longer supported.
 
+      The *k* argument is now optional.
+
 Discrete distributions
 ----------------------
 
diff --git a/Lib/random.py b/Lib/random.py
index c70294ee0cbf08..25ad83af37de9c 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -349,7 +349,7 @@ def shuffle(self, x):
             j = randbelow(i + 1)
             x[i], x[j] = x[j], x[i]
 
-    def sample(self, population, k, *, counts=None):
+    def sample(self, population, k=None, *, counts=None):
         """Chooses k unique random elements from a population sequence.
 
         Returns a new list containing elements from the population while
@@ -406,6 +406,8 @@ def sample(self, population, k, *, counts=None):
             raise TypeError("Population must be a sequence.  "
                             "For dicts or sets, use sorted(d).")
         n = len(population)
+        if k is None:
+            k = n
         if counts is not None:
             cum_counts = list(_accumulate(counts))
             if len(cum_counts) != n: