diff --git a/Lib/decimal.py b/Lib/decimal.py
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -547,7 +547,7 @@
 class Decimal(object):
     """Floating point class for decimal arithmetic."""
 
-    __slots__ = ('_exp','_int','_sign', '_is_special')
+    __slots__ = ('_exp','_int','_sign', '_is_special', '_hash')
     # Generally, the value of the Decimal instance is given by
     #  (-1)**_sign * _int * 10**_exp
     # Special values are signified by _is_special == True
@@ -577,6 +577,7 @@
         # digits.
 
         self = object.__new__(cls)
+        self._hash = -1
 
         # From a string
         # REs insist on real strings, so we can too.
@@ -988,6 +989,7 @@
         # agrees with the hash of a numerically equal integer, float
         # or Fraction, we follow the rules for numeric hashes outlined
         # in the documentation.  (See library docs, 'Built-in Types').
+
         if self._is_special:
             if self.is_snan():
                 raise TypeError('Cannot hash a signaling NaN value.')
@@ -998,6 +1000,8 @@
                     return -_PyHASH_INF
                 else:
                     return _PyHASH_INF
+        if self._hash != -1:
+            return self._hash
 
         if self._exp >= 0:
             exp_hash = pow(10, self._exp, _PyHASH_MODULUS)
@@ -1005,7 +1009,9 @@
             exp_hash = pow(_PyHASH_10INV, -self._exp, _PyHASH_MODULUS)
         hash_ = int(self._int) * exp_hash % _PyHASH_MODULUS
         ans = hash_ if self >= 0 else -hash_
-        return -2 if ans == -1 else ans
+        ans = -2 if ans == -1 else ans
+        self._hash = ans
+        return ans
 
     def as_tuple(self):
         """Represents the number as a triple tuple.