Kendall Jenner and Bella Hadid held hands and joined up with more than 25,000 people at the Pride Parade in London ... in matching rainbow cowboy hats.

The colorful gals took part in the annual march through central London -- now in its 45th year -- Saturday to celebrate the LGBTQ community. They also showed off their abs ... as a bonus.

London's mayor said the event was their biggest ever and is the "best antidote" to recent tragedies and terrorist attacks in England.