Agnes of Poitiers or Empress Agnes (c.1025-1077) was regent of the Holy Roman Empire from 1056 to 1068.

She was born to William V, Duke of Aquitaine and Count of Poitiers and his wife Agnes of Burgundy. She was the sister of Duke William VI, Duke Eudes, Duke William VII, and Duke William VIII.

Agnes married Henry III, Holy Roman Emperor, on November 21, 1043, at Besançon. Their children were:
1. Matilda of Germany, born 1045, married Rudolf von Rheinfeld.
2. Judith of Swabia, born 1047, married first King Solomon of Hungary, secondly to King Wladislaus I Herman of Poland.
3. Adelaide of Germany, born 1048, later Abbess of Quedlinburg.
4. Henry IV, Holy Roman Emperor, born November 11, 1050.
5. Conrad, born 1052, died young.

After her husband's death, Agnes served as regent during the minority of their young son, Henry IV. Her chief counselor was Henry, Bishop of Augsburg, who was widely hated for his arrogance and his suspected relationship with the empress. Although Agnes pursued a policy of reconciliation with her late husband's enemies, a conspiracy was formed against her by a cadre of power-hungry princes. Shortly after Easter 1062, her son Henry was abducted by some of these conspirators, who included the bishop of Cologne and the duke of Bavaria. Without her son, Agnes lost her political power and was forced into a temporary retirement. In 1065 she went to Rome, where she lived under the guidance of the theologian Peter Damian. In her later years Agnes acted as a peacemaker between her son Henry IV and his enemies.