The 25-year-old forward was an unrestricted free agent after not receiving a qualifying offer from the Boston Bruins.
"It came together pretty fast," Ritchie said. "The lure of Toronto and the team they have, and being from here and the fit I think they have for me, that was all part of it. I felt the Leafs were the best team and fit."
Ritchie grew up in Orangeville, Ontario, 50 miles from Toronto.
He scored 26 points (15 goals, 11 assists) in 56 games for the Bruins last season and four points (one goal, three assists) in 11 Stanley Cup Playoff games.
Selected by the Anaheim Ducks with the No. 10 pick in the 2014 NHL Draft, Ritchie has scored 137 points (59 goals, 78 assists) in 350 regular-season games with the Ducks and Bruins and nine points (six goals, three assists) in 38 playoff games.
The Maple Leafs signed
Ondrej Kase
to a one-year, $1.25 million contract Friday. Like Ritchie, the 25-year-old forward was an unrestricted free agent after not receiving a qualifying offer from Boston.
Kase did not score a point and was limited to three games for the Bruins last season because of injuries.
"I think he's doing a lot better and he's getting past the point and he's going to be able to stay healthy for a long period of time," Ritchie said about Kase. "The Leafs and the fans are going to love him."
Selected by Anaheim in the seventh round (No. 205) of the 2014 draft, Kase has scored 97 points (43 goals, 54 assists) in 207 games with the Ducks and Bruins and six points (two goals, four assists) in 24 playoff games.
Kase and Ritchie were traded to Boston by Anaheim three days apart on Feb. 21 and 24, 2020.
NHL.com independent correspondent Dave McCarthy contributed to this report
