The annual cycling festival will see thousands of enthusiasts take part in a host of events including a 100-mile ride from London to Surrey on Sunday.
The amateurs FreeCycle fun ride will be followed on a similar course by 150 professionals racing in the RideLondon-Surrey Classic.
Some roads and bridges on the route have been be closed for the events.
A number of roads in the City of London, Westminster, parts of the borough of Camden and Waterloo Bridge are closed from 06:00 BST to 18:00 on Saturday.
On Sunday, road closures will be in place from 04:00 in parts of east, central and south-west London ahead of the 100-mile race.
The event started at the Queen Elizabeth Olympic Park, then follows a 100-mile (160km) route on closed roads through the capital and into Surrey's countryside, before finishing on The Mall in central London.
From 10:30 onwards, roads along the route will be reopened in phases once the event has passed. All roads are expected to be open by 20:00.
London Bridge, Tower Bridge and Waterloo Bridge will be closed until the evening.
Transport for London has a full list of all roads and bridges affected.
More than 25,000 cyclists have descended on the capital this weekend for RideLondon.