|Lampėdžiai, Kaunas, Lithuania|
|Built by||Teutonic Order|
|Fate||Burned down in 1392|
|Events||Lithuanian Civil War (1389–92)|
Ritterswerder (German for "knight's ait") was a short-lived wooden castle built by the Teutonic Order in fall 1391. It was located on an island in the Neman River near Lampėdžiai, now part of the city of Kaunas.
The Order built the castle after they failed to capture Vilnius, capital of the Grand Duchy of Lithuania, in a five-week siege in September–October 1390. It became the headquarters of Vytautas, future Grand Duke of Lithuania, while he fought in the Lithuanian Civil War (1389–92) against his cousin Jogaila, King of Poland. In spring 1392, Henry of Masovia, Bishop of Płock, arrived to the castle to secretly negotiate an agreement between Vytautas and Jogaila. Here, about three weeks later, Henry married Rymgajla, Vytautas' sister, prompting many rumors and speculations. When the cousins reconciled, Vytautas turned against the Teutonic Order and burned Ritterswerder and two other Teutonic castles on the Neman River before returning to Vilnius.
During a campaign in 1394, the Order attempted to rebuild the castle but did not complete it as they were attacked by the Lithuanians. The Order decided to abandon the construction and besiege Vilnius for the second time. When in 1404, Vytautas confirmed the Peace of Raciąż in Kaunas, the Grand Master issued several documents from the island but did not mention the castle.
- Zinkus, Jonas; et al., eds. (1985–1988). "Ritersverderis". Tarybų Lietuvos enciklopedija (in Lithuanian). 3. Vilnius: Vyriausioji enciklopedijų redakcija. p. 555. LCC 86232954.
- Sužiedėlis, Simas, ed. (1970–1978). "Ritterswerder". Encyclopedia Lituanica. IV. Boston: Juozas Kapočius. p. 502. LCC 74-114275.
- Ivinskis, Zenonas (1953–1966). "Ritterswerder". Lietuvių enciklopedija (in Lithuanian). XXV. Boston: Lietuvių enciklopedijos leidykla. p. 348. LCC 55020366.
- Ivinskis, Zenonas (1978). Lietuvos istorija iki Vytauto Didžiojo mirties (in Lithuanian). Rome: Lietuvių katalikų mokslo akademija. p. 308. LCC 79346776.
- Urban, William (2006). Samogitian Crusade. Chicago: Lithuanian Research and Studies Center. pp. 208–209. ISBN 0-929700-56-2.