| Isaac J. MacCollum | |
| Office: | 11th Lieutenant Governor of Delaware |
| Term Start1: | January 21, 1941 |
| Term End1: | January 16, 1945 |
| Governor1: | Walter W. Bacon |
| Predecessor1: | Edward W. Cooch |
| Successor1: | Elbert N. Carvel |
| Birth Date: | 18 August 1889 |
| Death Place: | Wyoming, Delaware |
| Party: | Democratic Party |
| Residence: | Wyoming, Delaware |
| Alma Mater: | West Chester University |
| Profession: | Physician |
Isaac James MacCollum (August 18, 1889 – March 4, 1968) was an American physician and politician from Wyoming, in Kent County, Delaware. He was a member of the Democratic Party, and served as the 11th Lieutenant Governor of Delaware.
MacCollum was born at Fenwick Island, Delaware. He graduated from West Chester Normal School, now known as West Chester University, in 1910 and Jefferson Medical College in Philadelphia in 1914.
MacCollum served on the medical advisory board during World War I and was president of the Delaware State Medical Society in 1930. He served as a member of the trustees at Delaware State Hospital for nine years, president of the State Board of Health for four years, and a member of the State Parole Board for 20 years, 16 of those years as president.
He was elected Lieutenant Governor of Delaware in 1940, defeating Republican candidate Earle D. Willey of Dover, who was a Judge of the Court of Common Pleas. He served from January 21, 1941, until January 19, 1945, alongside Republican Governor Walter W. Bacon. In 1944 he ran for Governor against Bacon, but was defeated and returned to his medical practice full-time.
MacCallum died in Wyoming, Delaware. He was a respected country doctor, described as "mainly just a kind, traditional doctor. He made house calls, which is something you don't see today. I am grateful to him -- he delivered my first baby."
Elections are held the first Tuesday after November 1. U.S. Representatives take office January 3 and have a term of two years.
| Election results | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Year | Office | Subject | Party | Votes | % | Opponent | Party | Votes | % | ||||||||||
| 1940 | Lt. Governor | Isaac J. MacCollum | Democratic | Earle D. Willey | Republican | ||||||||||||||
| 1944 | Governor | Isaac J. MacCollum | Democratic | 62,156 | 49% | Walter W. Bacon | Republican | 63,829 | 51% | ||||||||||