What was the last territory in North Africa held by the Axis powers?

The last ground held by Axis forces in North Africa was an area in eastern Tunisia known as the Mareth Line. The Mareth Line consisted of a series of fortifications between the central coast of Tunisia and the Atlas Mountains. It was built by the French prior to the start of the war in anticipation of an Italian invasion. Axis forces had captured this area from the British along with the rest of Tunisia when they invaded the region in November of 1942. It was then placed under Italian administration and military control.
By the beginning of March in 1943, the British forces had begun their counteroffensive in North Africa. The British Eighth Army successfully outflanked Rommel's army at the Mareth Line and caught the remaining Axis forces in a pincer movement. Finding themselves outgunned with no hope of reinforcements or escape, over 275,000 Axis soldiers surrendered on May 13, 1943. With no Axis military forces left in North Africa, the remaining Italian colonies in Tunisia fell to Allied control. This marked the end of the Axis presence in North Africa.
http://www.bbc.co.uk/history/worldwars/wwtwo/launch_ani_north_africa_campaign.shtml

https://encyclopedia.ushmm.org/content/en/article/allied-military-operations-in-north-africa