Steve Martin's turning a lot of X users into amateur sleuths ... poking fun at speculation about Martin Short and Meryl Streep -- and, sending the internet into overdrive.

The comic actor shared a picture earlier Saturday from a Glamour article featuring the three of them ... crossing out his own face with a big red circle with a line through it.

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SM didn't add a caption to the post, letting fans speculate on his meaning ... and, they ran wild with the post -- wondering if this was Steve hard launching their relationship.

Obviously, it doesn't take a professional true crime podcaster to know Steve's just cracking a joke here ... he's getting the internet going as a goof -- probably not confirming the status of a relationship he's not part of.

Still, that didn't stop a ton of people online from claiming this was 100% real ... freaking out 'cause they think Steve's breaking the news about Meryl and Martin.

Of course, we don't know for sure what Steve's intention with the post was, so we've reached out to make sure we don't look like "The Jerk" in this situation. Quite frankly though, seems unlikely that this is a serious coming out for the pair.

Of course, Meryl and Martin have gotten fans' ears perked up ever since playing love interests on "Only Murders in the Building" ... with photos of them out together IRL fanning the flames of speculation.

Short previously said the two are just friends ... though that's not uncommon for celebs in this position.

Bottom line ... anything's possible on the dating front -- but, Steve probably ain't getting involved in his other two amigos' personal affairs.