Operation Devon was the code name of an amphibious landing by British Commandos in 1943 at Termoli, on the Adriatic coast of Italy, during the Italian Campaign of World War II.

Devon was launched on 3 October 1943, as part of the attack on the Volturno Line, and was undertaken by No. 3 Commando, No. 40 (Royal Marine) Commando and other elements of the 2nd Special Service Brigade. It was later reinforced by two brigades of the British 78th Infantry Division.

In the early hours of 3 October 1943, 3 and 40 Commandos, and elements of the Special Raiding Squadron landed behind the German lines under cover of darkness at Termoli, a seaport town on the Adriatic coast, north of the Biferno River. 40 Commando penetrated well into the town before the Germans were alerted.

There was brisk close-quarter fighting with German paratroopers from Kampfgruppe Rau – a defensive detachment made up of one Fallschirmjäger (paratrooper) platoon, with flak, engineer, transport and other support units from 1. Fallschirmjäger Division) ensued.

By 08:00 hours, the commandos had captured the town and controlled the approaches. So complete was the surprise that the kampfgruppe commander, Major Rau, was wearing pyjamas when captured, and German vehicles and motorcyclists drove into a commando ambush position until around noon.

Elements of the 78th Division, including tanks, had arrived to reinforce the commandos by the time German forces counter-attacked in strength: two battalions from 16. Panzer Division and the paratroopers of Kampfgruppe Schultz, The British held off repeated counter-attacks until 6 October. By noon on the 6th they had linked up with the British Eighth Army, and by noon on the 6th the enemy was in full retreat.

The operation was an success. It had won a valuable harbour and the assault force had repelled all counterattack. Devon subsequently caused German forces to withdraw from the natural defence line on the Biferno and denied them use of an important lateral road from Naples, thereby forcing them to retreat further northwards.

The operation had been a costly one for the commandos, however. Between them they lost three officers and 29 other ranks (ORs) killed, seven officers and 78 ORs wounded, and one officer and 22 ORs missing.