Jan Mayen (Urban East Norwegian: [jɑn ˈmɑ̀ɪən]) is a Norwegian volcanic island in the Arctic Ocean with no permanent population. It is 55 km (34 mi) long (southwest-northeast) and 373 km² (144 sq mi) in area, partly covered by glaciers (an area of 114.2 km² (44.1 sq mi) around the Beerenberg volcano). It has two parts: larger northeast Nord-Jan and smaller Sør-Jan, linked by a 2.5 km (1.6 mi) wide isthmus. It lies 600 km (370 mi) northeast of Iceland (495 km [305 mi] NE of Kolbeinsey), 500 km (310 mi) east of central Greenland, and 900 km (560 mi) northwest of Vesterålen, Norway. The island is mountainous, the highest summit being the Beerenberg volcano in the north. The isthmus is the location of the two largest lakes of the island, Sørlaguna (South Lagoon) and Nordlaguna (North Lagoon). A third lake is called Ullerenglaguna (Ullereng Lagoon). Jan Mayen was formed by the Jan Mayen hotspot and is defined by geologists as a microcontinent.

Although administered separately, in the ISO 3166-1 standard, Jan Mayen and Svalbard are collectively designated as Svalbard and Jan Mayen, with the two-letter country code "SJ".