Biggs, 24, has agreed a one-year deal at Kingston Park, having scored a club record 52 tries in 96 starts for Leeds.
He is also a regular England player on the world sevens circuit, helping them land the Wellington title earlier this year as well as reaching finals in Dubai and San Diego.
Newcastle rugby director Steve Bates coached Biggs when England Saxons won the Churchill Cup in America last year.
"The signing of top players like Tom provides a mark of where our ambition is right now," said Bates.
"Tom gives us a massive try-scoring threat on the wing.
"He is an extremely talented runner with an exceptional scoring record, he will cause problems for defences and provides serious cutting edge to what is shaping up to be a very strong squad for next season.
"This latest signing does not signal the end of our recruitment campaign, and we are working hard behind the scenes to add further quality to the squad in a number of positions."