Beata Łaska z Kościeleckich (1515-1576), was a Polish magnate heiress. She was reputed to be the illegitimate daughter of king Sigismund I the Old.
She was the daughter of Andrzej Kościelecki and Katarzyna Telniczanka and married to Illia Ostrogski (d. 1539) in 1539, and Olbracht Łaski in 1564. She served as maid-of-honour to queen Bona Sforza prior to her marriage. She was the mother of Elizaveta Ostrogska.
She is known for her famous feud with her son-in-law. She married her second spouse to have an ally against her son-in-law, but instead, her husband stole her fortune, had her imprisoned and committed bigamy. The case became a scandal and was brought before the emperor in a famed court case in 1573.