Benjamin Mackall IV (August 14, 1745–1807) was an American planter, lawyer, and jurist from Calvert County, Maryland. He served as a justice of the Maryland Court of Appeals from 1778 until 1806.
Benjamin was born into a very large and prosperous family, that of Colonel John James Mackall (1717–1772) and Mary (Hance) Mackall. Besides tobacco, they raised five sons and eight daughters. Benjamin was the second son, so he studied law and was admitted to the bar in 1765. He practiced law in both Calvert and several nearby counties.
On November 20, 1769 Mackall married Rebecca Potts in Annapolis, Maryland. She was the sister of Richard Potts who would later serve with Benjamin on Maryland's Court of Appeals. Although not the eldest son, he did inherit a small farm in Calvert County from his father, which he expanded to 1,620 acres (7 km²) by his death.
Mackall was first elected to the colonial House of delegates in 1768. He served there for a number of years. He was a member of all the sessions of the revolutionary house known as the Annapolis Convention, including the one that adopted the Maryland Constitution of 1776.