diff --git a/index.js b/index.js
index d35e240..3db2308 100644
--- a/index.js
+++ b/index.js
@@ -616,6 +616,15 @@
     ([Date_])
     (B (complement (isNaN)) (Number));
 
+  //# Descending :: Type -> Type
+  //.
+  //. [Descending][] type constructor.
+  var Descending = UnaryTypeWithUrl
+    ('Descending')
+    ([])
+    (typeEq ('sanctuary-descending/Descending@1'))
+    (I);
+
   //# Either :: Type -> Type -> Type
   //.
   //. [Either][] type constructor.
@@ -987,6 +996,7 @@
   //.   - <code>[Array](#Array) ([Unknown][])</code>
   //.   - <code>[Boolean](#Boolean)</code>
   //.   - <code>[Date](#Date)</code>
+  //.   - <code>[Descending](#Descending) ([Unknown][])</code>
   //.   - <code>[Either](#Either) ([Unknown][]) ([Unknown][])</code>
   //.   - <code>[Error](#Error)</code>
   //.   - <code>[HtmlElement](#HtmlElement)</code>
@@ -1006,6 +1016,7 @@
     Array_ (Unknown),
     Boolean_,
     Date_,
+    Descending (Unknown),
     Either_ (Unknown) (Unknown),
     Error_,
     HtmlElement,
@@ -2785,6 +2796,7 @@
     Boolean: Boolean_,
     Date: Date_,
     ValidDate: ValidDate,
+    Descending: fromUncheckedUnaryType (Descending),
     Either: fromUncheckedBinaryType (Either_),
     Error: Error_,
     Function: def ('Function') ({}) ([Array_ (Type), Type]) (Function_),
@@ -2923,6 +2935,7 @@
 
 }));
 
+//. [Descending]:           v:sanctuary-js/sanctuary-descending
 //. [Either]:               v:sanctuary-js/sanctuary-either
 //. [FL:Semigroup]:         https://github.com/fantasyland/fantasy-land#semigroup
 //. [HTML element]:         https://developer.mozilla.org/en-US/docs/Web/HTML/Element
diff --git a/package.json b/package.json
index 5b1d3de..ed99e30 100644
--- a/package.json
+++ b/package.json
@@ -20,6 +20,7 @@
     "sanctuary-type-identifiers": "2.0.x"
   },
   "devDependencies": {
+    "sanctuary-descending": "1.1.0",
     "sanctuary-maybe": "1.1.0",
     "sanctuary-pair": "1.1.0",
     "sanctuary-scripts": "3.2.x"
diff --git a/test/index.js b/test/index.js
index 8324e11..fe7018e 100644
--- a/test/index.js
+++ b/test/index.js
@@ -3,6 +3,7 @@
 const util = require ('util');
 const vm = require ('vm');
 
+const Descending = require ('sanctuary-descending');
 const {Left, Right} = require ('sanctuary-either');
 const {Nothing, Just} = require ('sanctuary-maybe');
 const Pair = require ('sanctuary-pair');
@@ -1512,6 +1513,20 @@ See https://github.com/sanctuary-js/sanctuary-def/tree/v${version}#Array2 for in
     eq ($.Date.supertypes) ([]);
   });
 
+  test ('provides the "Descending" type constructor', () => {
+    eq (typeof $.Descending) ('function');
+    eq ($.Descending.length) (1);
+    eq (show ($.Descending)) ('Descending :: Type -> Type');
+    eq (show ($.Descending (a))) ('(Descending a)');
+    eq (($.Descending (a)).name) ('Descending');
+    eq (($.Descending (a)).url) (`https://github.com/sanctuary-js/sanctuary-def/tree/v${version}#Descending`);
+
+    const isDescendingString = $.test ([]) ($.Descending ($.String));
+    eq (isDescendingString (null)) (false);
+    eq (isDescendingString (Descending (12.34))) (false);
+    eq (isDescendingString (Descending ('abc'))) (true);
+  });
+
   test ('provides the "Either" type constructor', () => {
     eq (typeof $.Either) ('function');
     eq ($.Either.length) (1);