diff --git a/docs/source/usersguide/input.rst b/docs/source/usersguide/input.rst
index d9b43c8214..3ce8934108 100644
--- a/docs/source/usersguide/input.rst
+++ b/docs/source/usersguide/input.rst
@@ -381,6 +381,14 @@ survival biasing, otherwise known as implicit capture or absorption.
 
 .. _trace:
 
+``<threads>`` Element
+---------------------
+
+The ``<threads>`` element indicates the number of OpenMP threads to be used for
+a simulation. It has no attributes and accept a positive integer value.
+
+  *Default*: None (Determined by environment variable :envvar:`OMP_NUM_THREADS`)
+
 ``<trace>`` Element
 -------------------