Lamar Odom has just been charged with 1 count of DUI ... TMZ has learned.

TMZ broke the story ... Lamar was arrested August 30 at 3:25 AM on the 101 Freeway after cops saw him driving too slow. He flunked several field sobriety tests and was then cuffed and taken to jail where he REFUSED to submit to a blood alcohol test.

The fact that he refused the blood alcohol test actually helped him ... in that normally a defendant would be charged with 2 counts of DUI -- driving under the influence and driving with .08 or higher.

Here's the bad news -- By refusing to take the test ... Lamar will have his driver's license suspended for 1 year.