The emerald-cut diamond ring is encircled by a distinct snake-like band, covered in several more tiny diamonds in a white-gold or platinum setting.
The diamond is an upgrade on Mirka's original engagement ring, which was a slightly smaller but still spectacular emerald-cut diamond.
In fact, it would appear Mirka has a wardrobe of engagement rings she can roll out for any occasion, like this stunning yellow diamond she wore to watch Federer play at Wimbledon in 2015.
The mother-of-four also attracted attention for her eye-catching outfit while attending the British tournament.
Clad in a pinstriped shirt and white denim mini, Mirka topped off her look with a crystal-encrusted Gucci butterfly belt.
The belt, priced at $950, was part of the Italian label's 2018 Cruise collection.
Mirka's husband's attire at Wimbledon is also attracting attention, but for a different reason.
A longtime Nike man, Federer is now kitted out in head-to-toe Uniqlo after recently signing a deal with Japanese mega-store rumoured to be worth $408 million over 10 years.