Mstislav III Glebovich was an Olgovichi prince. He was probably prince of Rylsk (1212–1239/1241) and of Chernigov (1235–1239/1241). During his reign, the Tatars invaded and pillaged the towns of the Principality of Chernigov.
- Position held
- Prince of Chernigov
- Born
- 1215, 1220
- Died
- October 1239
