Nick Cannon just made a shocking revelation … he was just 16 when he went to his first — now notorious — Diddy party … but he assures nothing happened!

Now 44 … the film and TV star made the eyebrow-raising announcement while chopping it up this week on “The Breakfast Club” when the topic of Diddy came up.

NC and podcast cohost Jess Hilarious both mentioned they had been to a Diddy party … once the hottest ticket in town — and now infamous amid the mogul’s mounting legal troubles … but each said nothing nefarious occurred.

DJ Envy and Charlamagne tha God were both blown away he was so young … but NC said he was being honest ’cause he had nothing to hide … and nothing happened … other than him dancin’ his ass off.

As TMZ reported this week … Diddy is awaiting his trial … now set for May … with the hip hop superstar facing a slew of federal charges of sex trafficking and racketeering.