Richilde, Countess of Hainaut
|Richilde, Countess of Mons and Hainaut, margraveness of Valenciennes|
|Died||(1086-03-15)15 March 1086
|Spouse(s)||Herman of Mons
Baldwin VI, Count of Flanders
William Fitzosbern, 1st Earl of Hereford
|Father||Reinier of Hasnon|
|Mother||Adelheid of Egisheim|
Richilde, Countess of Mons and Hainaut (c. 1018 – 15 March 1086), was a ruling countess of Hainaut from c. 1050 until 1076, in co-regency with her husband Baldwin VI, Count of Flanders and son Baldwin II, Count of Hainaut. She was also countess consort of Flanders by marriage to Baldwin VI, Count of Flanders. She served as regent of Flanders during the minority of her son Arnulf III, Count of Flanders in 1070-1071.
"Heiress of Hainaut"
For a long time, Richilde's own rights and position were not well understood. She is counted as ruling countess of Hainaut for different periods in different sources. In a first phase, she followed in the marche of Valenciennes c.1049 as only heir of her father, Reinier of Hasnon, who was installed in 1047 as margrave of Valenciennes to replace Baldwin V of Flanders (who rebelled against the Empire and lost his fiefs). Her first husband, Herman of Mons, count of Hainaut, died c.1050/1051, and left Richilde in the position of "heiress of Hainaut". As such,she was actually Countess regnant in her own right in Valenciennes and in her husband's rights in Hainaut.
Her position as "heiress of Hainaut", made her an attractive bride, but this placed the County in a dangerous position. She was forced by Baldwin V of Flanders to marry his eldest son Baldwin. It was indeed her future father-in-law Baldwin V who, under threat of force, arranged the marriage between his son and Richilde.
As Hainaut and Valenciennes were empirial fiefs and Henry III had not been consulted, the marriage resulted in a war between the emperor and the Baldwin's, ending in a total defeat of the latter in 1054. 
Her husband Baldwin became ruling count of Hainaut De jure uxoris. Her father-in-law also arranged to disinherite the two children she had with Herman, Hainaut and Valenciennes being inherited by the count of Flanders.
Baldwin VI followed as count of Flanders in 1067, unifying as such Hainaut, Valenciennes and Flanders, and ruled until his death (17 July 1070).
Regency of Flanders
Baldwin VI left Flanders to their eldest son, Arnulf III, and the County of Hainaut to the younger son, Baldwin II, with the provision that if either son preceded the other in death, he would inherit the other's county as well. Baldwin VI also obtained assurances from his brother Robert who gave his oath of homage and promised to protect his nephew. After Baldwin VI's death their son Arnulf III became Count of Flanders, but as he was a minor, Richilde served as Regent of Flanders.
Almost immediately Arnulf's uncle, Robert the Frisian, broke his oath to his brother Baldwin VI and disputed Arnulf's right to Flanders. Richilde asked for help from William Fitzosbern of Normandy who married her. Despite help from King Philip I of France, her forces were defeated at the Battle of Cassel and William Fitzosbern was killed along with her oldest son, Arnulf. Richilde herself was captured and released, King Philip later recognized Robert as Count of Flanders.
Richilde and her younger son, Baldwin II, retained Hainaut, but made subsequent unsuccessful attempts to recover Flanders. Richilde built the castle at Beaumont along with a chapel there dedicated to St. Venantius. She, along with her son Baldwin, founded the monastery of Saint-Denis-en-Broqueroie.
Richilde died on 15 March 1086.
Richilde married Herman, Count of Hainaut. They had two children:
- Roger (d. 1093) who was apparently lame, became Bishop of Châlons-sur-Marne.
- Daughter, whose name is unknown.
Richilde married secondly Baldwin VI, Count of Flanders. They were the parents of:
- Arnulf III, Count of Flanders (c. 1055 – 22 February 1071).
- Baldwin II, Count of Hainaut (c. 1056 – 1098).