Benjamin Grayson Orr (1762–1822) was the fourth mayor of Washington, D.C., elected by the council of aldermen in 1817 and serving for two years.

He was married to Elizabeth Flood, also of Virginia, and had lived for some time in Kentucky where in 1797 he was involved in a quarrel that led to a challenge to a dual that he did not accept.

He was elected an Alderman in 1812, but resigned one year later and became a supplier to U.S. Army brigades in Ohio and Michigan.

[3] As mayor, Orr procured public improvements such as grading of the streets and established Washington's first volunteer fire companies, appropriating $1,000 for the purchase of four fire bells and procured apparatus for the companies.

He also authorized a lottery to raise funds to build a penitentiary and city hall.