William Stewart Orr (21 January 1872 – 1944), known as Stewart Orr, was a Scottish watercolour artist and book illustrator.

Born in Glasgow, the son of William Orr, a merchant there, the young Orr was educated at the Glasgow School of Art.

In 1907, The Studio reviewed his work and commented "Stewart Orr, one of the younger men, is an artist with that rare quality, a sense of humour. This characteristic will be applicable in the role of book illustrator, in which the artist is actively engaged at the present time."

Orr married Mary Stuart Douglas and was elected a member of the Royal Watercolour Society in 1925. In 1927, Who's Who in Art described him as "water-colourist (chiefly), book illustrator occasionally"...