Shawne Merriman Kimberly Fattorini

Former NFL star Shawne Merriman has been ordered to pay up in a wrongful death lawsuit involving a Playboy employee who died of an overdose ... TMZ has learned.

According to court docs, obtained by TMZ, a Los Angeles judge entered a $4 million judgment against the former Chargers linebacker and three other defendants earlier this month over the 2017 death of Kimberly Fattorini.

The ruling comes after a jury found Merriman and the other defendants liable last year ... awarding Kimberly's parents, DeAnn and Ferdinand Fattorini, millions in damages.