"I want to thank the organisers and the wonderful crowd who made all the difference as we cycled by, helping to spur me on to finish the gruelling 100 miles in a respectable eight hours.
"Huge congratulations to everyone who took part
"RideLondon is now firmly on the map as one of the greatest cycling events in the world."
Mr Johnson, who battled with a puncture to complete the challenge in just over eight hours, was taking part in one of a number of events this weekend in what was billed as the UK's largest festival of cycling.
Mr Johnson said: "This is a great day for cycling, and for this city.
More top news
Services on major rail routes between London and south west England have been severely disrupted after a person was hit by a train.
The business executive, whose ruthless interviewing technique has won him many fans, is replacing Nick Hewer, who quit after a decade.
Recent opinion polls show Labour within striking distance of capturing the trophy seat of Finchley and Golders Green.