ruler of Lithuania, considered the founder of the Lithuanian state. He was also the first Lithuanian ruler to become a Christian.

Mindaugas successfully asserted himself over other leading Lithuanian nobles and tribal chiefs, including his brother and his nephews, in 1236. The state thus formed under his leadership included Lithuania proper, Samogitia, and much of Belorussia (Belarus). In 1250 or 1251 Mindaugas accepted baptism from the Livonian Knights (Brothers of the Sword, Order of the), thus easing western pressure against his state from the Teutonic and Livonian Knights and from Daniel of Halich-Volynia. In 1253 he received a royal crown from Pope Innocent IV.

With the west for a time stabilized, Mindaugas continued his eastern expansion into Russian lands, which he had begun in the 1230s. His efforts led to the incorporation of much Russian territory into Lithuania at the expense of Russia's Mongol subjugators. Indeed, Mindaugas' campaigns in the east checked a Mongol drive toward the Baltic.

Mindaugas turned his attention to the west again in the late 1250s, when the Livonian Knights encroached on Samogitia, causing a local revolt. Mindaugas unofficially supported the Samogitians and reverted to paganism. In 1263 he and two of his sons were murdered by a group of Samogitian rivals.