| Reginar IV | |
| Count of Mons | |
| Spouse: | Hedwig of France |
| Issue: | Reginar V, Count of Mons Lambert of Mons Beatrix |
| Noble Family: | Reginar |
| Father: | Reginar III, Count of Hainaut |
| Mother: | Adela |
| Birth Date: | 950 |
| Death Date: | 1013 (aged about 63) |
Reginar IV, Count of Mons, in Hainaut, (c. 950–1013) was the son of Reginar III and Adela. His father died in exile in Bohemia in 973.
His father, Reginar III, was exiled in 958 as a rebel by Otto I, Holy Roman Emperor. Hainaut was held after then by Godfrey I, Duke of Lower Lorraine, but Reginar IV claimed that Mons in Hainaut had been his father's.
He attacked Mons in 973, after the death of Duke Godfrey, but did not manage to hold it, because Godfrey I, Count of Verdun then held it until he died. He managed to replace Godfrey as Count of Mons in 998.
Regnier IV married Hedwig, daughter of Hugh Capet and Adelaide of Poitou.
They had: