William Zajíc of Valdek and Židlochovice (died 1 November 1420) was a Bohemian nobleman and politician.

After the war, William Zajíc re-entered the service of Jobst, this time in a diplomatic position.

William Zajíc participated in diplomatic negotiations in Prague at the court of Wenceslas IV.

After the death of Margrave Jobst in 1411, William Zajíc entered the service of King Wenceslas IV.

In 1420, William Zajíc took part in Sigismund's campaign in Bohemia and the siege of Prague before the Battle of Vítkov Hill.