The mission - HMS Albion's first deployment of 2021 - was the largest gathering of NATO naval power in the Baltic region this year.
The Littoral Response Group (North) deployment saw Royal Marines and amphibious ships HMS Albion and RFA Mounts Bay – supported at times by Type 23 frigate HMS Lancaster – work across the region.
The deployment culminated in the Baltops war games, where forces from 18 countries trained together.
Plymouth-based Albion led the UK task group on the major exercises – which also included US-led training along the Norwegian coastline – as the Royal Navy continued to shape how British commando forces, centred on the Royal Marines, will operate in the future by testing tactics and equipment.
Captain Simon Kelly, Task Group Commander and Commanding Officer of HMS Albion, said: "Since leaving Plymouth in April, we have conducted amphibious training around the coast of Scotland, participated in a major exercise off the coast of Norway and operated in the Baltic Sea region.
"We have developed the Royal Navy’s commando force concepts, shaping how Royal Marines will operate in the future by trialling new tactics and equipment."
The mission was HMS Albion's first in the Baltic since 2019 and completed visits to Finland, Lithuania and Latvia as well as training closely with Swedish and Finnish forces before Baltops began.
Albion briefly stopped off in Leith, Scotland, to offload vehicles on her way back to Plymouth.