In an interview with Die Zeit, Hitzlsperger said that "only in recent years" had he realized he "would rather be with a man."
Capped 52 times by Germany, Hitzlsperger retired from the game in September after a difficult run of injuries and form. He said he had stepped back from the spotlight since but was now ready to speak about his sexuality as he wanted "to advance the discussion to homosexuality among professional athletes." He said the issue of homosexuality in football had for too long been "simply ignored."
"In England, Germany or Italy [where Hitzlsperger played] the issue of homosexuality is not treated seriously - at least, not in the dressing room," he said.
Hitzlsperger is the first prominent male German footballer to publicly come out since former Rot-Weiss Essen midfielder Marcus Urban revealed his homosexuality in 2007. Urban, who walked away from the game after he became sick of hiding his sexuality, told German newspaper Die Welt in 2007 that, at the time, he knew of at least three gay Bundesliga footballers.
Former United States international midfielder Robbie Rogers is one of the few current male players to have announced his homosexuality. The Los Angeles Galaxy player made headlines when he came out February 2013.
It has been far more common in women's football, with former Germany international and now administrator Steffi Jones having come out the same month as Rogers. US star Abby Wambach - the FIFA Women's World Player of the Year in 2012 - married fellow player Sarah Huffmann in October.
Hitzlsperger had emerged as one of Germany's brightest prospects after debuting for English Premier League club Aston Villa in 2001, aged 19.
Dubbed 'Der Hammer' for his penchant for powerful, long-range goals, the left-footed Hitzlsperger moved back to his homeland in 2005 with Stuttgart. Part of the club's Bundesliga-winning campaign in 2006/07, he spent two seasons as the club's captain before falling out of favor under head coach Markus Babbel.
A move to Italian club Lazio in the January transfer window of 2010 followed - the first of several unspectacular stops as his career ground to a halt. Hampered by persistent injuries, Hitzlsperger had four clubs in just three-and-a-half seasons before departing his final club, English outfit Everton, at the end of the 2012/13 campaign.
Internationally, Hitzlsperger was part of Germany squads at the 2006 World Cup, Euro 2008 and the 2005 Confederations Cup. He played the last of his 52 caps for his country in August 2010, having scored six goals.
Hitzlsperger said he had informed Germany head coach Joachim Löw and team manager Oliver Bierhoff of his intentions to come out before making it publicly known.
Praise for Hitzlsperger
The announcement on Wednesday was met with praise across Germany.
"We live in a country where no one should be afraid to acknowledge his sexuality [because of intolerance]," Chancellor Angela Merkel's spokesperson, Steffen Seibert said in Berlin.
Her former foreign minister, Guido Westerwelle, also praised Hitzlsperger's courage.
"[He] deserves the highest respect," he told Zeit Online, calling the move something that's "easier said than done." Westerwelle was himself one of Germany's first politicians to come out.
An outpouring of praise also emanated from Germany's soccer league, with positive and supportive statements from both its president and its national coach.
Germany coach Joachim Löw called on fans to respect Hitzlperger's decision to come out, adding that "only the athletic performance and social behaviour of a player is important."
DFB president Wolfgang Niersbach recalled him as a noteworthy player and individual during his time in the Bundesliga.
"Thomas was always a role model for whom I had the utmost respect - and now this respect has grown even more," Niersbach said.