Disgraced ex-Bayern Munich president Uli Hoeness was released from prison on Monday after serving 21 months for tax evasion, a regional official said.

The 64-year-old served half of his 3.5-year sentence after being convicted in March 2014 of having evaded at least 28.5 million euros ($31.5 million) in taxes.

His release in the middle of the night was confirmed by ­Bavaria's justice ministry, which gave no further details.

Hoeness, the son of a German butcher, rose to fame as the driving force behind Bayern's rise and became a millionaire businessman before his fall from grace.

He was granted day release in January 2015 and immediately started working in the club's youth academy.

"It's not over!" was Hoeness's battle cry to FC Bayern in May 2014, shortly before starting his sentence.

Hoeness has said he will announce his future plans on July 1.

The date coincides with the start of Carlo Ancelotti's reign as Bayern's coach to replace Pep Guardiola.

Hoeness's first public engagement is expected to be at a ceremony in Moenchengladbach on March 13 to honor Jupp Heynckes, who coached Bayern to the 2013 treble.

Three days later, he will be at Munich's Allianz Arena to watch Bayern's Champions League last-16 second leg at home against Juventus.

Bayern's Honorary Chairman Franz Beckenbauer told Bild daily on Monday that Hoeness will likely have a role in the club.

"He is as always full of enthusiasm for Bayern. Uli should switch off first before coming back. In whichever function, Bayern needs him," the soccer legend said.

During his playing career, Hoeness was a central midfielder at the heart of the Bayern team which won the European Cup three times in 1974-76.

A persistent knee injury forced the 1974 World Cup winner to retire at just 27, when  he became the club's youngest-ever manager.

When Franz Beckenbauer stood down as Bayern president in 2009, Hoeness succeeded him after a 30-year apprenticeship.

But behind the scenes, he was obsessively gambling ­millions on stocks and currencies via his Swiss bank accounts.