The flag has never previously been flown at Faslane (Picture: Royal Navy).
The rainbow flag has been hoisted at HM Naval Base Clyde for the first time.
February is LGBT History Month and the last Friday of the month is called Purple Friday, which is marked in Scotland to show solidarity with young LGBT people.
Representatives from the Royal Navy, Ministry of Defence and Police Scotland all gathered to watch the flag being hoisted up 43 Commando’s main flagpole.
Sub Lieutenant Annabel Sykes, 28, from West Yorkshire said: "It was a huge honour to represent the Royal Navy at the raising of the Pride Flag at HMNB Clyde for the first time today, to mark Purple Friday.
"Together with our civil service colleagues and industry partners, we are leading the way to promote an inclusive culture and celebrate the diversity of our people at the home of the UK Submarine Service."
Gavin Leckie, who works for a commercial partner of the Ministry of Defence, Babcock Clyde, said:
"This symbolic gesture by the Naval Base Commander marks another milestone in LGBT+ history.
"My hope is that all who visit the base will recognise this senior commitment to the wider inclusivity agenda, which Babcock is proud to support, and become an ally of the LGBT+ community."
In 2019 the Royal Navy was ranked as the 15th best employer for LGBT people in Stonewall's survey of 100 employers for its Workplace Equality Index.
The previous year the Senior Service had been ranked in 32nd place.