Eleanor of Guzman (ca 1310 – 1351) was a mistress of King Alfonso XI of Castile. She is known in Spanish as Leonor Núñez de Guzmán.

She was born in Seville, daughter of the Castilian nobles Pedro Núñez de Guzmán (descendant of the noble family of Saint Dominic) and Juana Ponce de León (great-granddaughter of King Alfonso IX of León), and sister of Alfonso Núñez de Guzmán (ca 1300 – Gibraltar, 1342), Master of the Order of Santiago, married ca 1330 to Dona Dona María de La Cerda, 1st Lady of Villafranca de Valcárcel (ca 1290 –), without issue.

Eleanor and Alfonso had ten children:

• Pedro Alfonso of Castile, 1st Lord of Aguilar de Campoo (1330 - 1338).
• Juana Alfonso of Castile, 1st Lady of Trastamara (born 1330).
• Sancho Alfonso of Castile, 1st Lord of Ledesma (1331 - 1343).
• Enrique Alfonso of Castile, 1st Count of Trastamara (1334 - 1379), in future king Henry II of Castile.
• Fadrique Alfonso of Castile, Master of the Order of Santiago and 1st Lord of Haro; (born 1335).
• Fernando Alfonso of Castile, 2nd Lord of Ledesma.
• Tello Alfonso of Castile, 2nd Lord of Aguilar de Campoo (born 1337).
• Juan Alfonso of Castile, 1st Lord of Badajoz and Jerez de la Frontera (1341 - 1359).
• Sancho Alfonso of Castile, 1st Count of Alburquerque (born 1342).
• Pedro Alfonso of Castile (1345 - 1359).