The cat’s out of the bag ... Mick Fleetwood has gone and tied the knot for a fifth time ... and he spilled the news himself by dropping honeymoon pics!

The 78-year-old Fleetwood Mac drummer looks totally smitten in a series of sun-soaked snaps from the South Pacific ... planting a kiss under a hat on his 56-year-old bride Elizabeth Jordan, whose face he kept hidden.

He also shared some dreamy ocean shots, captioning them all about love, sunshine and "moments to be remembered" -- man’s clearly in full honeymoon mode.

Mick’s been with Elizabeth for 6 years and got engaged last year -- so this one’s been a long time coming ... fingers crossed Number 5 sticks!

As for his track record -- it’s been a ride … multiple marriages -- including model Jenny Boyd, twice -- plus that infamous Stevie Nicks affair during the making of "Rumours" ... before a couple more marriages that didn’t quite go the distance.

Congrats to the couple!!!