William Rathbone IV (10 June 1757 – 11 February 1809) was a member of the noted Rathbone family of Liverpool, England. He was the son of William Rathbone III and Rachel Rutter, and was a Liverpool ship-owner and merchant, involved in the organisation of American trade with Liverpool.

In 1786 Robert Benson joined with William Rathbone IV of the existing house of William Rathbone & Co. to form Rathbone & Benson, a Liverpool business trading mainly with America.

Originally a member of the Society of Friends, he felt compelled to write a Narrative of Events in Ireland among the Quakers in 1786 in protest against religious intolerance in the Society, for which he was disowned from the Society in 1805. He would never join another religious body, though he occasionally worshiped with local Unitarian congregations.

As a committed opponent to slavery, he was a founder member of the Liverpool Committee for the Aboliton of the Slave Trade.

He married Hannah Mary, (1761–1839) daughter of Richard Reynolds of Bristol and Hannah (née Darby) at the Friends Meeting House, Shrewsbury. They had eight children:

William Rathbone V (1787–1868)
Richard Rathbone (1788–1860)
Hannah Mary (1791–1865)
Joseph (1793–1794)
Theophilus (1795–1798)
Theodore Woolman (1798–1863)
Benson (1800–1834)
Basil (1802–1804)

In 1788, he leased the family house and estate of Greenbank, then part of the Toxteth Park estate, to serve as a country retreat for his young family, and purchased the freehold of the house in 1809.

Rathbone died on 11 February 1809, and was buried at Liverpool Friends' Burial Ground.