The 30-year-old ended months of speculation by agreeing to a two-year deal with the recent World Club Challenge winners.
"I have been blessed to play professional football in Newcastle for the last 13 years, and I am extremely grateful for the support I have received throughout my career from everyone involved at the Knights," Buderus said.
"This is an opportunity to broaden my life and rugby league experiences while fulfilling career ambitions of playing in England."
Buderus made his first grade debut in 1997, and has gone on to forge an outstanding NRL career spanning 205 matches.
He has won 24 Test caps and represented NSW 18 times, captaining the Blues in every Origin series since 2004.
Leeds coach Brian McClennan said Buderus was the first player he thought of when it came to recruiting an NRL star.
"I thought that was an area that the club could develop in the future, with a two-pronged dummy half attack," McClennan said.
"Danny Buderus is the best hooker in Australia and I am excited about seeing him team up with Matt Diskin.
"The prospect of Danny working alongside Matt Diskin, Rob Burrow, Danny McGuire and Brent Webb is an exciting one for everyone connected with the Rhinos."
Newcastle chief executive Steve Burraston said Buderus had the full backing of the club in making his decision to head overseas.
"When you think of the names synonymous with our club, Danny Buderus is at the top of the list," Burraston said.
"He represents everything Newcastle is about and has nothing left to prove.
"He's achieved everything the game has to offer and earned his place in rugby league history as one of the greatest players of all time.
When Danny indicated he would like to finish his career in England we did everything we could to make it happen."