The 90th Perthshire Light Infantry was a Scottish light infantry regiment of the British Army, raised in 1794. Under the Childers Reforms it amalgamated with the 26th (Cameronian) Regiment of Foot to form the Cameronians in 1881.

The 26th (Cameronian) Regiment of Foot was an infantry regiment of the Scots Army and subsequently a Scottish infantry regiment of the British Army, active from 1689 to 1881. Although the regiment took the name of its first colonel as The Earl of Angus's Regiment, it became popularly known as The Cameronians until 1751, when it was ranked as the 26th Foot. Under the Childers Reforms it amalgamated with the 90th Regiment of Foot to form the Cameronians in 1881. The Cameronians were themselves disbanded in 1968, meaning that no Army unit today perpetuates the lineage of the 26th Foot.