Mstislav I Vladimirovich the Great (Мстислав Владимирович Великий in Russian) (June 1,1076 — April 14,1132), Grand Prince of Kiev (1125-1132), the eldest son of Vladimir Monomakh by Gytha of Wessex. He figures prominently in the Norse Sagas under the name Harald, taken to allude to his grandfather, Harold II of England.

As his father's future successor, Mstislav reigned in Novgorod the Great from 1088-93 and (after a brief stint at Rostov) from 1095-1117. Thereafter he was Monomakh's co-ruler in Belgorod-on-the-Dnieper, and inherited the Kievan throne after his death. He built numerous churches in Novgorod, of which St Nicholas Cathedral (1113) and the cathedral of St Anthony Cloister (1117) survive to the present day. Later, he would also erect important churches in Kiev, notably his family sepulchre at Berestovo and the church of Our Lady at Podil.

Mstislav's life was spent in constant warfare with Cumans (1093, 1107, 1111, 1129), Estonians (1111, 1113, 1116, 1130), Lithuanians (1131), and the princedom of Polotsk (1127, 1129). In 1096, he defeated his uncle Oleg of Chernigov on the Koloksha River, thereby laying foundation for the centuries of enmity between his and Oleg's descendants. Mstislav was the last ruler of united Rus, and upon his death, as the chronicler put it, "the land of Rus was torn apart".

In 1095, Mstislav wed Princess Christine of Sweden, daughter of King Ingold I. They had many children:

1. Ingeborg of Kiev, married Canute Lavard of Jutland, and was mother to Valdemar I of Denmark
2. Malmfrid, married (1) Sigurd I of Norway; (2) Eric II of Denmark
3. Eupraxia, married Alexius I Comnenus
4. Vsevolod of Novgorod
5. Maria, married Vsevolod II of Kiev
6. Iziaslav II of Kiev
7. Rostislav of Kiev
8. Sviatopolk of Pskov
9. Rogneda, married Yaroslav of Volinya
10. Xenia, married Briachislav of Izyaslawl

Christine died on January 18, 1122; later that year Mstislav married again, to the daughter of Dmitry Zavidich, a nobleman of Novgorod. Their children were:

1. Vladimir II Mstislavich (1132-1171)
2. Euphrosyne of Kiev, married King Geza II of Hungary