Alexander Macdonell of Collachie (1762 – March 18, 1842) was a soldier and political figure in Upper Canada.
He was born in Scotland in 1762 and arrived in the Mohawk Valley of New York with other members of his family, including his brother, Angus Macdonell of Collachie.
He served with the Royal Highland Emigrant Regiment during the American Revolution.
Macdonell moved to York (Toronto), where he served as a Sheriff for the Home District from 1792 to 1805.
He was elected to the 3rd Parliament of Upper Canada representing Glengarry & Prescott, serving until 1816.