The tiny Mediterranean nation have been battling for membership of European football's governing body since 1999.
Their application was initially rejected by UEFA, but the Gibraltar Football Association (GFA) took their case to the Court of Arbitration for Sport (CAS) - who ruled in their favour.
Gibraltar was granted provisional membership last October, facing fierce opposition from Spain, and now they have been admitted at the UEFA congress.
UEFA president Michel Platini declared a "vast majority" of nations voted in favour of Gibraltar joining.
As full members they will be eligible to compete in the qualifying stages for the European Championship in 2016.
Their club sides will also be allowed to compete in the UEFA Champions League and Europa League.
Platini also confirmed that Gibraltar would be kept apart from Spain in qualifying for Euro 2016.
Platini said: "Gibraltar will not play qualifying matches with Spain - we also have this situation with Armenia and Azerbaijan.''
Source: Newcastle United Mad