The 90th Regiment of Foot (Perthshire Volunteers) was a Scottish infantry regiment of the British Army, active from 1794 to 1881.
The 90th was raised in 1794 for service during the French Revolutionary Wars, and later the Napoleonic Wars. In the post-war period the regiment saw action in South Africa, serving in the 7th and the 9th Xhosa Wars. For this service they won two battle honours, "South Africa 1846-7", and "South Africa 1877-8-9".
In 1881, as part of the Childers Reforms, the 90th Regiment was amalgamated with the 26th Regiment and became the 2nd Battalion Cameronians (Scottish Rifles).