A saltire, also called Saint Andrew's Cross or the crux decussata, is a heraldic symbol in the form of a diagonal cross. The word comes from the Middle French sautoir, Medieval Latin saltatoria ("stirrup").

From its use as field sign, the saltire came to be used in a number of flags, in the 16th century for Scotland and Burgundy, in the 18th century also as the ensign of the Russian Navy, and for Ireland. Notable 19th-century usage includes some of the flags of the Confederate States of America. It is also used in the flag of Jamaica and on seals, and as a heraldic charge in coats of arms.

The term saltirewise or in saltire refers to heraldic charges arranged as a diagonal cross. The shield may also be divided per saltire, i.e. diagonally.

A warning sign in the shape of a saltire is also used to indicate the point at which a railway line intersects a road at a level crossing.