Jada Pinkett Smith is putting a giant Hollywood rumor to bed about her own bed ... she and husband Will Smith don't screw around with other couples.

Jada was promoting her new flick, "Girls Trip," on 'Watch What Happens Live' when a caller asked what the craziest rumor is that Jada's ever heard about herself. It took a second before Jada laughed off that it was one about her and Will being Hollywood's notorious swingers.

Funny thing is ... Jada made it sound like the door to the bedroom could be open to other couples in the future.

One thing she did come clean on though ... how she and Will have remained together for 23 years, which is no easy feat in Hollywood.