 His reign also saw the gradual decline of the Union of Sweden and Norway, which culminated in its dissolution in 1905.He was subsequently succeeded as King of Norway by his grandnephew Prince Carl of Denmark under the regnal name Haakon VII, and as King of Sweden by his eldest son, Gustaf V.

Oscar II is the paternal great-great-grandfather of Carl XVI Gustaf, King of Sweden since 1973.Harald V, King of Norway since 1991, is a great-grandson of Oscar II, through his third son Prince Carl, Duke of Västergötland.