Levi Johnston has been ordered to pay nearly $18,000 in back child support ... TMZ has learned.




During a hearing in the child support case between Bristol Palin and Levi, the judge ruled Levi must pay $1,688.42 a month in support, retroactive to the child's birth -- December 27, 2008.

Bristol was in court in Alaska for the hearing -- Levi was a no-show.

Bristol's lawyer, Thomas Van Flein, tells TMZ, "Bristol is pleased with the court rulings today and looks forward to resolving the remaining issues with Levi."