Princess Teresa of León (1080 – November 11 1130) was an illegitimate daughter of king Alfonso VI of Castile and Leon. In 1096 she married Henry of Burgundy, first Count of Portugal while on crusade into Spain. The county of Portugal was part of her dowry, so Henry settled down and became count or duke of Portugal (during this period he is thought to have changed his name to Henri / Henrique).

At first Henri was a vassal of his father-in-law, but when Alfonso died in 1109, leaving everything to his daughter Urraca, Henri invaded Leon, hoping to add to his lands. When he died in 1112, Teresa was left to deal with the mess. Although their son Afonso I of Portugal, the first king of Portugal (aka: Alfonso I Henriques) succeeded to the countship, he was young and was therefore placed under his mother's tutelage. She took on the responsibility as regent and governed her land that had only recently been reconquered from the Moors and only as far as the Mondego.

In an effort to expand the land that would descend to her son, in 1116 Teresa fought her half-sister and queen, Urraca. She fought again in 1120, and in 1121 when she was besieged and captured at Lanhoso. A negotiated peace, aided by a couple of archbishops, was arrived at including terms that Teresa would go free and hold the county of Portugal as a fief of Leon.

Teresa tried to retain the rule of the County, even after her son's majority. Over the course of five years she lavished wealth and titles on her lover, Fernando Peres, count of Trava. These actions estranged her other son, who was the archbishop of Braga, and the nobles, who were mostly foreign crusaders. By 1128 her sons and nobles were fed up. Alfonso was named sole ruler; he defeated her troops near Guimaraes and took her prisoner. She was deposed and exiled (some sources say to a convent, other say with Peres). She died in 1130.

Sources of Information: Rulers of Spain, 718-1153