The Portugal international moved to the Allianz Arena from Benfica last summer. The 20-year-old impressed for his national side as they went on to win the European championship in 2016, which saw him top clubs across Europe interested in signing him.
Since moving to Bayern, Sanches struggled to impress for Carlo Ancelotti's side. He made only six starts in his debut season in the Bundesliga and failed to score a goal or register an assist in 25 matches played in all competitions last term.
Lack of playing time saw him linked with a move away from his current employers. Manchester United and Chelsea, along with Liverpool were reportedly interested in securing the midfielder's services, reported talkSPORT.
In addition to this, AC Milan were also believed to be in the race for his signature. However, no deal took place, despite Rummenigge earlier confirming interest from Antonio Conte's Chelsea in signing Sanches. The Bayern chief has now confirmed the midfielder will join Swansea on a season-long loan deal.
"We wanted Renato Sanches to join a club, where he is able to play on a high level and where he has a coach, which wants him" Rummenigge told German publication Kicker.
"Renato has to play continuously for a year, and that's not guaranteed given the quality in our squad."
Rummenigge had earlier revealed that Bayern will allow Sanches to leave on a permanent transfer if the interested clubs can meet their €48m (£44.3m, $57.1m) asking price. Failure from clubs to meet their evaluation has forced the former Benfica star to join Swansea on loan.
Kicker also claims Swansea will pay a loan fee of €8.5m (£7.8m, $10.2m) to Bayern and the Welsh club will not have an option to make the deal permanent next summer. At the Liberty Stadium, Sanches will play under Paul Clement, who was Carlo Ancelotti's assistant at Real Madrid and Bayern Munich.