| Beatrice de Montfort | |
| suo jure Countess of Montfort-l'Amaury Countess of Dreux Countess of Braine | |
| Birth Date: | December 1248 – December 1249 |
| Birth Place: | France |
| Death Date: | 9 March 1312 |
| Spouse: | Robert IV, Count of Dreux, Braine and Montfort-l'Amaury |
| Issue: | Marie of Dreux Yolande of Dreux, Queen of Scotland John II, Count of Dreux and Braine Jeanne of Dreux, Countess of Braine Beatrice of Dreux, Abbess of Port-Royal Robert of Dreux, Seigneur of Chateau-du-Loire |
| Father: | John I of Montfort |
| Mother: | Jeanne, Dame de Chateaudun |
| Noble Family: | House of Montfort |
Beatrice de Montfort, Countess of Montfort-l'Amaury (December 1249 – 9 March 1312) was a ruling sovereign countess of Montfort from 1249 until 1312. She was also countess of Dreux by marriage to Robert IV, Count of Dreux. She was the ancestor of the Dukes of Brittany from the House of Montfort-Dreux which derived its name from her title.
Beatrice was born sometime between December 1248 and 1249, the only child of John I of Montfort, Count of Dreux and Jeanne, Dame de Chateaudun.
In 1249, Beatrice's father died in Cyprus, while participating in the Seventh Crusade. Thus, Beatrice succeeded her father as ruling countess of Montfort at the age of about one year old.
In 1251, Jeanne married her second husband, John II of Brienne, Grand Butler of France. Jeanne and John had a daughter, Blanche de Brienne, Baroness Tingry (1252–1302); Blanche married William II de Fiennes, Baron of Tingry. Jeanne died sometime after 1252, leaving Beatrice and her half-sister Blanche as her co-heiresses.
Beatrice was married to Robert IV, Count of Dreux, Braine and Montfort-l'Amaury in 1260, when she was about eleven years old. He was the son of John I, Count of Dreux and Braine, and Marie de Bourbon. As was the custom for female rulers at this point in time, he became the co-ruler with Beatrice and Count of Montfort by right of his wife after their wedding.
Beatrice died on 9 March 1312 at the age of around sixty-three. She was buried in the Abbaye de Haute-Bruyère.
Beatrice and Robert had:
. Michelle Bubenicek . Quand les femmes gouvernent: droit et politique au XIVe siècle:Yolande de Flandre, Droit et politique au XIV siecle . French . Ecole des Chartes . 2002 .
. Douglas Richardson . Kimball G. . Everingham . David . Faris . Plantagenet Ancestry: A Study in Colonial and Medieval Families, Royal Ancestry series . Genealogical Publishing Co. . 2004 .