The SKIMS founder took to her IG Stories Tuesday, shedding light on Mason's new Instagram page, which was officially launched over the weekend ... and which has already amassed hundreds of thousands of followers. Also ... you can clearly see the kid is all grown up (ish).

Alongside a screenshot of Mason's new account, Kim wrote ... "I still can't believe Mason is on IG. Everyone follow my nephew @masondisick." Pretty straightforward, and it seems people heeded her request.

KK's call to action certainly appears to have made an impact, as the 14-year-old's IG account now boasts well over 600,000 followers ... although it's hard to say if it was all Kim's doing.

Either way ... this is certainly the most we've seen of Mason in recent years. Remember, Mason took a large step back from the limelight when he was a pre-teen, choosing not to appear on the family's reality show, "The Kardashians," or in their social media posts.

Kourtney explained Mason's MIA status in a 2022 episode of "The Kardashians," noting in a confessional ... "He does not like it. He doesn't want any part of it. He's not on social media. He doesn't love it, and I want my kids to be kids. I crave normalcy as much as we can have it."

Occasionally, Mason would be spotted in the background of Kourtney or his dad Scott Disick's uploads ... but not much outside of that -- until now, that is. He's already got a few posts up.

The famous teen has seemingly changed his tune ... as Kim probably wouldn't have drawn attention to his social media if he wasn't open to it. Of course, Kim wasn't the only member of the KarJenner brood to promote Mason's new social media presence.

Khloe shared the first photo Mason posted online to her own Instagram Stories, writing ... "I can't believe my @masondisick is on insta. The one who named us KiKi and KoKo is a legit teenager."