The Croation made it official with Nokaut.com:

"I have no motivation left and it's time to leave. Thank you all for supporting me."

I've been a fan of Mirko for years, for not only providing exciting fights throughout his career.  However, the most impressive thing about him to me is that he fought the best of the best for most of his career.  There are very few 'cans' on his resume so to speak, and he sported one of the best knockout weapons of all time.  The left headkick in which we'll pay tribute to after the jump.  However, I just wanted to rundown the list of who's who that Mirko has fought during his career:

Fedor Emelianenko, Antonio Rodrigo Nogueira, Josh Barnett(3x), Gabriel Gonzaga, Sakuraba, Kevin Randleman, Aleksander Emelianenko, Mark Coleman, Wanderlei Silva, Igor Vovchanchyn, and Heath Herring.  Check out a great highlight that contains some of his K-1 stuff as well after the jump.  It justifies what he brought to MMA when he made the jump from kickboxing.  Great stuff.

[Note by Kelvin Hunt, 09/24/09 2:38 PM EDT ]MMA4Real reader Wlad brought it to our attention earlier today.  However, this link suggests that Mirko has not retired.  This isn't unusual as it's a similar situation to the he said/she said stuff after UFC 99.  I guess we'll know that Mirko hasn't retired when we see him in the octagon again.