| Honorific-Prefix: | The Hon. |
| Joseph-Octave Arsenault | |
| Office1: | Senator for Prince Edward Island, Prince Edward Island |
| Appointed1: | Mackenzie Bowell |
| Term Start1: | February 18, 1895 |
| Term End1: | December 14, 1897 |
| Office2: | Member of the Legislative Assembly of Prince Edward Island for 3rd Prince |
| Term Start2: | 1873 |
| Term End2: | 1895 |
| Birth Date: | 5 August 1828 |
| Birth Place: | Cascumpec, PEI |
| Death Place: | Abrams Village, PEI |
| Party: | Conservative |
| Children: | Aubin-Edmond Arsenault Joseph-Félix Arsenault |
Joseph-Octave Arsenault (August 5, 1828 – December 14, 1897) was a Canadian politician who was the first Acadian from Prince Edward Island to be named to the Senate of Canada.
Born in Cascumpec, Prince Edward Island, the son of Mélème Arsenault and Bibienne Poirier, he was a teacher, and later the owner of several businesses, including two general stores and a fish company. In 1867, he was elected to the Legislative Assembly of Prince Edward Island for the riding of 3rd Prince and served for 28 years. In 1895, he was appointed to the Senate representing the senatorial division of Prince Edward Island. He served until his death in Abram-Village in 1897.
In 1861, he married Gertrude Gaudet. They had nine children. His son Aubin-Edmond Arsenault was Premier of Prince Edward Island and his son Joseph-Félix Arsenault served in the provincial assembly.
Arsenault played an important role in organizing the first two Acadian national conventions which were held in Memramcook, New Brunswick in 1881 and Miscouche, Prince Edward Island in 1884.