Lamar Odom -- FINISHED in Dallas

Stick a fork in Lamar Odom ... 'cause he's officially DONE in Dallas.

Odom released a statement explaining he will "step away from the team" ... effective immediately.

He added, "I'm sorry that things didn't work out better for both of us, but I wish the Mavs' organization, my teammates and Dallas fans nothing but continued success in the defense of their championship."

According to ESPN, Odom will leave the team ASAP ... but he will not be cut.

Instead, Odom will be listed as "inactive" for the rest of the season ... which means he could still be traded after the season.

Odom has been downright atrocious this season -- he's put up career low numbers and just hasn't appeared motivated on the court.

Sucks even worse for his wife Khloe Kardashian ... because the couple had just leased a condo in Dallas and had planned to begin shooting footage for the family reality show.