| Office: | Governor−General of Toungoo |
| Term Start: | October 1375 |
| Term End: | January 1376 |
| Predecessor: | Pyanchi I |
| Successor: | Pyanchi II |
| Ma Sein Burmese: | |
| Death Date: | January 1376 Pyatho 737 ME |
| Death Place: | Toungoo (Taungoo) |
| Allegiance: | Hanthawaddy Kingdom |
| Serviceyears: | ? − 1376 |
| Rank: | Commander |
| Branch: | Royal Hanthawaddy Army |
Ma[1] Sein (Burmese: မစိန်, in Burmese pronounced as /maʔ sèiɴ/) was a Hanthawaddy commander who occupied Toungoo (Taungoo) for three months in 1375−76. The ethnic Mon commander was posted in Toungoo by King Binnya U of Hanthawaddy upon request of Viceroy Pyanchi I of Toungoo in order to raise a rebellion against Ava. His army was in charge of Toungoo in 1375 when Pyanchi I was assassinated near Prome (Pyay) by pro-Ava forces.[2] The commander claimed the state of Toungoo on behalf of Hanthawaddy, and resisted the subsequent siege by Pyanchi I's son Pyanchi II and son-in-law Sokkate for three months. He was put to death when the siege was broken three months later.[3] [4]