They pedalled through London, Cardiff, Manchester and Bristol yesterday in the event’s 16th outing.
The cyclists were rallying against car culture – with many ladies and fellas wearing just helmets, shoes and rucksacks.
In one snap, a woman cycles through central London in the buff with “love nature” written across her chest.
Another topless rider cycles past the gates of Buckingham Palace with a defiant hand in the air.
In London, cyclists started at eight locations across the capital and congregated in the centre.
In Cardiff, cyclists took off from the city’s university and pedalled around the city centre.
Over in Manchester, hundreds of riders took over the city’s streets on a day when temperatures failed to creep higher than 14C in the north west.
The event’s organisers posted on their website: “Even when we are fully clothed we are naked to the danger of motorists on the road.
“We want to live in a world not blighted by traffic pollution”
“We want to live in a world not blighted by traffic pollution where the car is seen as the go to form of transport.
“Most of all we are here to celebrate people, who come in all shapes and sizes and are beautiful as they are.”
Last year, thousands of naked cyclists took to the streets of Sao Paolo in Brazil to criticise the lack of bike lanes.
The protesters were pushing for safer roads and decorated themselves with paint.