Rapper Tyga has pledged his commitment to girlfriend Kylie Jenner by gifting her with a huge diamond promise ring.

Kim Kardashian's youngest sister has been spotted with a new piece of jewellery on her left ring finger in recent days, sparking renewed speculation the on/off couple is set to wed.

Kylie took to Snapchat on Thursday (08Sep16) to show off the flashy oval-shaped diamond, revealing it was a present from her man, but he hasn't proposed just yet.

"If this is a promise ring, I want to know what my engagement ring is gonna look like," she captioned the picture, in which Kylie is shown resting her hand on Tyga's, as he also shows off an oversized diamond-studded ring.

It's the first sign the on/off couple is getting serious about marriage, after previously dismissing wedding speculation on a handful of occasions.

If the rapper, 26, does eventually decide to pop the question, it will make for a very interesting family dynamic, as his ex-fiancee Blac Chyna, the mother of his three-year-old son King Cairo, is currently engaged to Kylie's brother, Rob Kardashian, and expecting his child.

Model Blac and Rob went public with their new romance in January (16), and they became engaged in April (16), days before announcing they were starting a family.

Chyna and Tyga began dating in 2011, after she appeared in his Rack City music video, and they became engaged in 2012. They split in 2014.