Joseph Patrick O'Neil (December 27, 1863 – July 27, 1938) was a United States Army officer in the late 19th and early 20th centuries.

He served in several conflicts, including World War I. Joseph O'Neil was born in Brooklyn, New York, on December 27, 1863, the son of Mary Ann Burke and Major Joseph O'Neil, a Union Army veteran of the American Civil War.

As a member of the Oregon Alpine Club, he advocated for the exploration of Mount Olympus, which was finally permitted by General John Gibbon.

In summer 1890 O'Neil led the expedition and reached the summit of the southern peak on September 22, 1890.

[1] With the United States' involvement in World War I in August 1917 Joseph O'Neil was promoted to brigadier general of the National Army.