its is both
That would be the River Thames.
The River Thames is the major river through London, cutting right through the middle of the city. There are many other rivers in London, such as the River Lee (or Lea) and the River Brent.
The river Thames (pronounced temz)
London is situated on the River Thames (pronounced 'temz'.
There is no Province of Yukon River. The Yukon territory is in Canada's northwest corner and name is connected to the aboriginal name for the major river flowing through it and Alaska.
Thames River
The Thames flows through London.
The River Thames has multiple confluences. One such is the confluence of the River Thames and the River Darent at Dartford.
The river Thames.
The river Thames is in England.
River Thames.