Andreas Hinkel has decided to hang up his boots at age 30 after a career that saw him play in Spain's La Liga, the Bundesliga and the Scottish Premier League.
The full-back played for Freiburg last season, but managed only seven appearances for the German club.
He started his career by coming through the ranks at Stuttgart before moving on to Sevilla in 2006, where he was part of the squad that won the UEFA Cup in 2007 and the Copa del Rey. He then moved to Celtic in 2008.
The Germany international made the announcement on his blog.
"There's something important I need to tell you," Hinkel said.
"I have decided to end my career as footballer.
"It was not a snap decision, but a step that has been planned for some time. I've even been busy with my new career for a few weeks already.
"I know many may think that 30 is no age to quit, but in my case I have a different opinion.
"I played football at a very high level for 12 years - 12 wonderful intensive years with amazing experiences, first class clubs and overwhelming supporters."
The right back then expressed an interest in staying involved with football to some degree going forward.
"I am thrilled to begin a new chapter in my life and full of energy to start it," he added.
"It goes without saying that this chapter will also be in football, this is the best sport in the world.
"I have several ideas, but before I can start to implement them, I want to improve my skills and knowledge in all respective areas. Right now I'm working to get a coaching licence."
Hinkel made 180 appearances in Europe's top divisions and scored two goals. He was also capped 21 times for Germany.