Alekna Sudimantaitis (Belarusian: Алехна Судзімонтавіч, Polish: Olechno Sudymuntowicz; died in 1490/1491) was an influential Lithuanian noble of Trąby coat of arms, Grand Chancellor of the Grand Duchy of Lithuania (1478–1490) and Voivode of Vilnius (1477–1490).
Alekna is mentioned in written sources in 1446. He was royal cup-bearer (cześnik, 1448–1477) and chamberlain (podkomorzy; 1449–1453). According to the Bychowiec Chronicle, Alekna led a Lithuanian squad in the 1454 Battle of Chojnice. During the battle Alekna was taken captive by the Teutonic Knights. He was also starosta of Hrodna (1458–1459) and regent of Polatsk (1463–1477). After the death of Mykolas Kęsgaila in 1476, Alekna became Grand Chancellor and Voivode of Vilnius. He held those positions until his death in 1490 or 1491; the positions were taken over by Alekna's relative Mikalojus Radvila the Old. In 1482, a brevis from Pope Sixtus IV to launch a new crusade against the Ottoman Turks was addressed to Alekna and Martynas Goštautas, Voivode of Trakai.
He considered Hozhevo (Belarusian: Хожево) near Maladzyechna and Ratomas near Minsk as his patrimony. He also held territories near Hrodna and in Tureysk (Russian: Турейск). Through his wife, Alekna inherited Dokshytsy. From Grand Duke Casimir, Alekna received Smalyavichy, Voupa, Ostroshitsy (Belarusian: Астрошыцы). He funded an altar inside a chapel of Vilnius Castle Complex, where his wife Jadvyga was buried. It is likely that he was buried there as well.
Biased works of Jan Długosz claimed that Alekna was of "humble lot," when in fact Alekna hailed from an established noble family. He was a son of Sudimantas Dargaitis and second cousin of Mikalojus Radvila the Old (see family tree in Astikai). He married Jadvyga, daughter of Jonas Manvydas. They had five daughters:
- Sophia, wife of Alexander Olshanski
- Alexandra, wife of Mikołaj Tęczyński – one of first known marriages of a Lithuanian noblewoman to a Polish nobleman
- Daughter of unknown name, wife of Stanislovas Kęsgaila
- Jadviga, wife of Jonas Kontautaitis, Stanislovas Mantautas, and Stanislovas Kęsgaila
- Anna, a Cistercian nun
- Petrauskas, Rimvydas (2003). Lietuvos diduomenė XIV a. pabaigoje – XV a. (in Lithuanian). Aidai. p. 297. ISBN 9955-445-67-X.
- Petrauskas, Rimvydas; Jūratė Kiaupienė (2009). Lietuvos istorija. Nauji horizontai: dinastija, visoumenė, valstybė (in Lithuanian) IV. Baltos lankos. p. 208. ISBN 978-9955-23-239-1.
- Petrauskas, Rimvydas (2003). Lietuvos diduomenė XIV a. pabaigoje – XV a. (in Lithuanian). Aidai. p. 145. ISBN 9955-445-67-X.
- Petrauskas, Rimvydas (2003). Lietuvos diduomenė XIV a. pabaigoje – XV a. (in Lithuanian). Aidai. p. 100. ISBN 9955-445-67-X.
- Gudavičius, Edvardas (2010). "Alekna Sudimantaitis". Lietuva (in Lithuanian) II. Mokslo ir enciklopedijų leidybos centras. p. 32. ISBN 978-5-420-01667-1.