Bergenhus len was an administrative division of the Kingdom of Norway that existed from 1503 to 1662, with the Bergenhus Fortress in Bergen as its administrative center Norwegian administrative division. The "len" was changed to an "amt" (district) in 1662 but it kept its original name and capital until 1919.
History.
Formerly, in Norway, the term "len" (plural "len") represents an administrative region whose borders roughly match those of the counties of today. It was an essential part of the national administration during the years when the two kingdoms of Denmark and Norway were united as a single kingdom. At the beginning of the 16th century the political divisions were variable but, since 1503, there were four main "slottslen" (castle provinces), each with about 30 smaller sub-divisions. They were: 
Until 1660, their headquarters were, respectively, Akershus Fortress, Bohus Fortress, Bergenhus Fortress and the fortified city of Trondheim. The sub-divisions corresponded to the present church districts of the Lutheran Church of Norway.
In 1536, North Norway was added to the "len" of Bergenhus but the "len" still had about 30 sub-divisions. In 1560, they were:
They covered the areas of the modern Vestland county (previously Hordaland and Sogn og Fjordane). Trondheim and North Norway were still parts of the Bergenhus len. Since then, the number of the "len's" sub-divisions was gradually reduced as the provincial and national administrations both became more stable. By 1660, Bergenhus was one of Norway's nine main "len", each with 17 sub-divisions.
On 19 February 1662, by royal decree, all the "len", including Bergenhus, were renamed as "amt" (plural "amt"), and their "lenmann" were recast as the "amtmann", both from "Amt", the German word for "office", reflecting the bias of the Danish court of that year.
In 1671, Norway was divided once more, this time into four principal "amt" or "stiftsamt" and nine subordinate "amt". Bergenhus amt was the "stiftsamt" and its subordinate "amt" were Halsnøy klostergods, Hardanger amt and Nordlandene amt.
In 1763, Bergenhus was divided in two, creating the following "amt" – Nordre Bergenhus amt and Søndre Bergenhus amt.
In 1919, Nordre Bergenhus "amt" was renamed as Sogn og Fjordane "fylke" (county) and Søndre Bergenhus "amt" became Hordaland "fylke", and each of their "amtmann" were retitled as a "fylkesmann" (country governor). In 2020, the counties of Hordaland and Sogn og Fjordane merged into the new Vestland county.