The Pet Shop Boys are among those headlining the event at Preston Park, which was started with a parade through the city.
Other acts appearing at the ticketed event at the end of the route include Years & Years, Louisa Johnson and David Morales.
The event is marking 50 years since the partial decriminalisation of homosexuality in England and Wales.
The first Brighton and Hove gay Pride march was staged in 1973, but did not return to the city until 1991 amid political anger over Section 20's ban of the promotion of homosexuality.
The streets of Brighton are a rainbow of colours as the city celebrates Pride.
The festival began with a show-stopping display by the Princess of Wales' Parachute Regiment, which performed a freefall parachute jump to deliver the rainbow flag to Hove Lawns.
Huge crowds gathered on the seafront in glorious sunshine to watch the parade get under way.
At least 100 floats were taking part this year with some amazing psychedelic costumes on show to celebrate the Summer of Love theme.
I spotted Police and Crime Commissioner Katy Bourne having a great time as she walked with Sussex Police towards the front of the parade.
And one of the biggest cheers from the crowd was for Brighton's famous 'oldest gay in the village' George Montague, now 94, as he sailed past on his scooter.
Assistant Chief Constable Laurence Taylor, of Sussex Police, said: "Months of preparation have taken place in the lead up to Pride and, as in previous years, public safety is our main priority."
About 300,000 people have gathered in Brighton for the annual Pride event.