In divorce documents printed on TMZ, Khloé blamed "irreconcilable differences".
The Keeping Up With The Kardashians star, 29, is being represented by sister Kim's former attorney Laura Wasser and has asked to have Odom dropped from her surname, according to the website.
She married basketball player Lamar, 34, in 2009 - just four weeks after they met.
Their marriage became troubled earlier this year amid allegations of the basketball star's repeated drug use and infidelity, but Khloé has kept a dignified silence throughout.
The final straw was said to have come for Khloé when a bizarre rap video of Lamar openly bragging about cheating on her was posted online on November 22.
The next day, Khloé was spotted without her wedding ring, and has since ditched it for good.
On Thursday, she walked the red carpet at the Hollywood Reporter's Women In Entertainment Breakfast in Los Angeles without the ring.
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