A mystery donor gave £5.5m to the BBC's Sport Relief appeal, pushing the total raised for vulnerable people in the UK and abroad to more than £19m.
Chiles and Shearer cycled for 26 hours
After announcing the donation during Friday's live BBC broadcast, presenter Patrick Kielty said: "Wherever you are tonight, you are amazing."
Organisers said it was a telephone donation and the sum was the largest in Comic Relief's 22-year history.
Karl Reynolds of Sport Relief said it was a "phenomenal and humbling" act.
"The generosity of this gift is overwhelming," said Mr Reynolds, who is head of fundraising at the charity.
"And along with all the other donations it will ensure that Sport Relief can continue to do life-changing work in the UK and in some of the poorest countries in the world."
Shearer visited Uganda to see Sport Relief work
A spokeswoman said no-one at Sport Relief knew the identity of the donor but it was phoned through during the BBC telethon.
It edged the total towards the £20m mark, although that is expected to be surpassed on Sunday when thousands of people are due to run a mile to raise more funds.
Last year's total on the night was £10m and grand total £18m.
Although yet to be confirmed as such, the £5.5m donation is thought to be the largest given to any telethon in the UK.
In 2000, racehorse owner Robert Hitchins celebrated his Ascot win by donating a million pounds to Children in Need.
That sum was matched by Scottish philanthropist Sir Tom Hunter six years later.
The theme of this year's Sport Relief was "Rise To The Challenge".
Former England footballer Alan Shearer and BBC presenter Adrian Chiles cycled 335 miles from Newcastle to London in two days.
There were Sport Relief-themed editions of Strictly Come Dancing and The Apprentice, and there was a celebrity boxing bout in which GMTV presenter Ben Shephard beat soul singer Lemar.
Jonathan Ross interviewed Michael Parkinson and last week, Little Britain star David Walliams and Olympic rower James Cracknell "swam to Africa" - covering the 12 miles from Gibraltar to Morocco.