Heynckes functions of the head coach "Bavaria" will play until the end of the 2017-2018 season, and to your duties, the German will start from Monday, 9 October.
After winning the German title in 2016/17, Ancelotti was sacked last week in the wake of Bayern's 3-0 Champions League defeat to Paris Saint-Germain.
JUPP HEYNCKES is back as manager of Bayern Munich. "He's the ideal coach for FC Bayern at this moment in time". We are convinced that he is exactly the right man to lead the team back into success in the current situation and to achieve our goals.
Despite his age, Heynckes says he feels "fit" enough to coach Bayern, who he led to the Champions League, Bundesliga and German Cup treble in 2013.
"I would not have returned to any other club in the world, but Bayern Munich is close to my heart", said Heynckes, vowing to transform the team back into a "successful" squad.
"It's not a comeback, it's [because of] friendships, and I've only done it because I have a lot to thank Bayern for", Heynckes told Kicker.
Ancelotti left in September with Bayern third in the Bundesliga, five points behind leaders Borussia Dortmund.
Heynckes was brought in on the basis that he would steady the ship until the end of the season after Carlo Ancelotti's sacking. "I'm looking forward to it".
The 72-year-old veteran manager had on Thursday confirmed to Rheinische Post, a local paper near his home that Bayern president Uli Hoeness and chief executive Karl-Heinz Rummenigge have asked him to return. Guardiola failed to win the Champions League in his three seasons, while Ancelotti's side was outclassed by eventual champion Madrid last season.