The YMS-15 Gyan is a mobile suit that appears in the TV anime Mobile Suit Gundam.

The YMS-15 Gyan was developed by the Zimmad company in the late stages of the One Year War for the Principality of Zeon's second phase main mobile suit development project. It was designed with exceptional close combat ability in anticipation of melee combat against the Earth Federation's mobile suits. When needed, the Gyan can receive fire support from the MS-09B Doms or MS-09R Rick Doms. However, its focus on close combat resulted in lower versatility and this contributed to its loss to the Zeonic's MS-14 Gelgoog.

A Gyan (depending on sources, this is either the sole unit produced or one of three produced units) was later customized for use by Colonel M'Quve of the Mobile Assault Force. A powerful beam saber serves as Gyan's primary weapon, it also has a shield with 60 needle missiles and 25 hide bombs (space mines) for laying traps. The appearance of the Gyan, with its silver armor and Pickelhaube helmet design, has a strong resemblance to a medieval armored knight. This is further emphasized by M'Quve's fighting style, which is heavily based on fencing.