The Livonian Brothers of the Sword (Latin Fratres militiae Christi, literally the "brothers of the army of Christ"), also known as the Christ Knights, Sword Brethren or The Militia of Christ of Livonia, was a military order started in 1202 by Albert von Buxhövden, bishop of Riga (or Prince-Bishop of Livonia), and composed of German "warrior monks". It was primarily based on the rules of the Templars.

Since its founding, the order tended to ignore its supposed vassalage to the bishops. In 1218 the bishop asked for help from the Danish king, Valdemar II—but Valdemar arranged a deal with the Sword Brothers and conquered the north of Estonia.

The Sword brethren headquarters were at Viljandi (Fellin) in Estonia, where the walls of the Grandmaster's castle are still standing. Other strongholds included Cesis (Wenden), Sigulda (Segewold) and Aizkraukle (Ascheraden). The commanders of Viljandi (Fellin), Kuldiga (Goldingen), Aluksne (Marienburg), Tallinn and the bailiff of Paide (Järva) belonged to the 5-member entourage of the Order's Grandmaster.

The Lithuanians and Semigallians defeated the Brothers at the Battle of Siauliai in 1236. Next year the order joined with the Teutonic Knights of Prussia, switching to their rules but maintaining administrative independence in their conquered lands. Between 1288 and 1290 they managed to conquer all of Courland and Livonia. In 1346 the united orders bought the rest of Estonia from Valdemar IV Atterdag, king of Denmark.

With the decline of the Teutonic Order by the middle of the fifteenth century, the Sword Brothers decided to resume their independence. During the Livonian War the order was defeated by Russian troops in the Battle of Ergeme in 1560. The Order sought protection from the Polish king Sigismund II Augustus who had already in 1557 intervened in a war between the bishop of Riga and the Brothers.

After an agreement with the Polish king and his representatives (especially Mikołaj 'Czarny' Radziwiłł) the last grandmaster of the order, Gotthard Kettler secularized the order and converted to the Lutheran Church. In the southern part of the Brothers' lands he created a Duchy of Courland and Semigalia. Most of the other lands were seized by Poland-Lithuania. The north of Estonia was taken back by Denmark and Sweden.

Masters of the order include:

• Wenno 1204–1209
• Volquin 1209–1236
• Hermann Balk 1237–1238
• Dietrich von Grüningen 1238–1242
• Dietrich von Grüningen 1244–1246
• Andreas von Stierland 1248–1253
• Anno von Sangershausen 1253–1256
• Burchard von Hornhausen 1256–1260
• Werner von Breithausen 1261–1263
• Konrad von Mandern 1263–1266
• Otto von Lutterberg 1266–1270
• Walther von Nortecken 1270–1273
• Ernst von Rassburg 1273–1279
• Konrad von Feuchtwangen 1279–1281
• Wilken von Endorp 1281–1287
• Konrad von Herzogenstein 1288–1290
• Halt von Hohembach –1293
• Heinrich von Dinkelaghe 1295–1296
• Bruno 1296–1298
• Gottfried von Rogga 1298–1307
• Conrad von Jocke 1309–1322
• Johannes Ungenade 1322–1324
• Reimar Hane 1324–1328
• Everhard von Monheim 1328–1340
• Burchard von Dreileben 1340–1345
• Goswin von Hercke 1345–1359
• Arnold von Vietinghof 1359–1364
• Wilhelm von Vrymersheim 1364–1385
• R. von Eltz 1385–1389
• Wennemar Hasenkamp von Brüggeneye 1389–1401
• Konrad von Vietinghof 1401–1413
• Diderick Tork 1413–1415
• Siegfried Lander von Spanheim 1415–1424
• Zisse von Rutenberg 1424–1433
• Franco Kerskorff 1433–1435
• Heinrich von Bockenvorde 1435–1437
• H. Vinke von Overbergen 1438–1450
• Johann Osthoff von Mengede 1450–1469
• Johann Wolthuss von Herse 1470–1471
• Bernd von der Borch 1471–1483
• Johann Fridach von Loringhofe 1483–1494
• Wolter von Plettenberg 1494–1535
• Hermann Hasenkamp von Brüggeneye 1535–1549
• Johann von der Recke 1549–1551
• Heinrich von Galen 1551–1557
• Johann Wilhelm von Fürstenberg 1557–1559
• Godert (Gotthard) Kettler 1559–1561

See also

• Courland, Livonia, Latvia, Estonia, Teutonic Knights, Order of Dobrin