Topptur - literally summit trip - is the Norwegian word for what English-speaking skiers usually call ski-touring or randonee: climbing a mountain on alpine touring skis (typically wider and shorter than fjellski) using removable climbing skins for grip on the up, then skiing the descent on the same equipment after the skins come off. The bindings are releasable in alpine mode for the descent and pivot at the toe in touring mode for the climb. The boots are stiff plastic shells with a walk/ski mechanism.
Norway is one of the most respected ski-touring destinations in Europe, with two distinct regional traditions. The Lyngen Alps east of Tromsø offer serious technical sea-to-summit terrain - climbs of 1,000 to 1,500 meters directly from fjord-level water to glaciated alpine summits, often with significant avalanche complexity in the maritime snowpack.
The Sunnmøre Alps further south are mostly toured on guided days from fjord hotels and mountain lodges around the Hjørundfjord and Stranda. A couple of operators also run a ski-and-sail variant, with a boat as the base and the climb starting at the fjord edge, but it is a niche, and very few guests stay aboard. Both Lyngen and Sunnmøre traditions require certified mountain guides - the Norwegian Tindevegledere or the international UIAGM/IFMGA equivalent - and the Norwegian Mountain Code applies in full.
What separates topptur from langrenn and fjellski is terrain steepness and technical descent. Cross-country and traditional fjellski are about distance across moderate terrain. Topptur is about vertical - the up-and-down day, often 1,000+ meters of climbing, on technical alpine ground. The equipment costs more, the avalanche risk is higher, the rewards are different. The right window for Norwegian topptur is mid-March to early May; the season has limited overlap with cross-country, which peaks in January-February.