William Marriott Canby Sr. (1831–1904) was an American banker, business executive, philanthropist and botanist.

He is famous as a leading expert on the flora of Delaware and the "eastern shore" region of Maryland[3][2] and as an epistolary correspondent with Charles Darwin concerning insectivorous plants.

[5] After education at the Friends School at Westtown and from private tutors,[3] William Marriott Canby conducted several successful businesses in Wilmington, Delaware.

Henry Marriott Canby married Edith Dillon Mathews (born 1835 in Zanesville, Ohio) on 15 July 1870.

Wilmington's Rockford Park has a memorial dedicated to William Marriott Canby Sr.