The broadcaster was synonymous with both events, hosting the televised charity fundraiser and providing a cutting commentary for the pan-continental talent show for 35 years.
His role in both programmes made them essential viewing for generations of viewers and helped cement his reputation as one of the warmest and wittiest stars of British television.
Sir Terry was a trustee of the Children in Need charity for many years, before becoming its life president in November 2010.
Its chief executive, David Ramsden, paid tribute to the man who had “been at the heart of the charity for over 30 years raising millions to change the lives of children.”
In his final turn as presenter of the annual telethon in 2014, the programme raised a then-record total of more than £32m.
Gaby Roslin, who co-presented the show alongside Sir Terry for more than a decade, said she was in “total shock” at his death.
She tweeted: “Goodbye my cheeky chum. Forever in our hearts.”
A spokesman for the Eurovision Song Contest described him as the “most remarkable” commentator in the event’s history.
Sir Terry helmed the BBC’s coverage from 1973 to 2008 and became known for his deadpan one-liners.
He finally got a chance to present the programme proper in 1998, taking to the stage alongside Ulrika Jonsson in Birmingham after the UK’s Katrina And The Waves won Eurovision the previous year in Dublin.
His successor as Britain’s commentator and fellow Radio 2 presenter, Graham Norton, said of Sir Terry: “He made it seem effortless and for a young boy in Ireland he made it seem possible. RIP Sir Terry Wogan. I’ll raise a glass during song 9.”