William Harrison Jr. (c. 1750 – July 21, 1789) was an American planter from Charles County, Maryland. He was a delegate for Maryland in the Continental Congress of 1786 and 1787.

Harrison was an active revolutionary in Charles County. He served in the local militia, and as a representative in 1775 to the state's revolutionary assembly, the Annapolis Convention. In 1778 he was named as a justice of the peace for Charles County, and reappointed regularly until 1785.

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  • United States Congress. "William Harrison Jr. (id: H000280)". Biographical Directory of the United States Congress.