Gay Pride 2011, which adopts a funfair theme this year, kicks off from Custom House Square at 2pm.
Numbers are expected to surpass last year's crowds, which saw 15,000 walk alongside floats on the official route - up Royal Avenue, around the City Hall, down Castle Place and back to a family area at its starting point.
Alliance leader David Ford has given the event his full backing and congratulated organisers on the festival's success, which has seen several gay-themed events held across the city in the run-up.
He said: "Belfast Pride is an exciting event and I want to wish everyone who is taking part well.
"Belfast Pride and groups associated with the event help greatly in tackling prejudice and this is essential to help build the genuinely shared society that Northern Ireland needs and deserves. It promotes respect and ensures diversity is celebrated."
Lord Mayor Niall O Donnghaille will join the parade around the City Hall.
Founder member PA MagLochlainn said: "The carnival theme is a chance for everyone to dress up and enjoy themselves at what is the most orderly parade in Northern Ireland."
Belfast Gay Pride has been running for over 20 years, with support growing from 100 participants in 1991 to 15,000 last year. Belfast Pride ranks in the top 10 largest gay pride parades in the UK. Headlining the show in Custom House Square this year will be former Steps singer Lisa Scott-Lee. Boy George will make an appearance in Mynt/Yello Nightclub. Belfast Pride is organised by volunteers.
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