Snoop Dogg says he's giving up the smoke for good ... an activity that's been synonymous with his career since day one -- but, frankly, it's hard to tell if this is legit or not.

The Doggfather shocked his IG followers on Thursday with the PSA ... "After much consideration & conversation with my family, I've decided to give up smoke. Please respect my privacy at this time." On its face, it's a serious announcement ... it ain't 4/1 today.

Fans struggled to wrap their hands around the announcement in the comments -- Snoop without the chronic is like the ying without the yang ... and many figured he was just switching to edibles to keep his lungs clear.

Snoop's quit smoking before -- circa the release of his 2002 "Paid tha Cost to Be da Bo$$" -- but the sabbatical was short-lived as he entered his Snoop Lion era a few years later. He explained this in a sit-down around that time ... saying he simply couldn't quit the ganja.

Ironically his 'Mac & Devin' pal Wiz Khalifa recently announced the complete opposite -- increasing his smoke intake in favor of ditching alcohol altogether.

It may be an uphill battle -- Snoop just recently flicked a pic of his heavily stuffed ashtray less than a week ago ... but maybe he was just preparing for the detox.