Glen Arm is an unincorporated community in Baltimore County, Maryland, United States.

[1] Glen Arm lies along what is now Glen Arm Road, which was once part of Old Harford Road, one of the early routes used for conveying agricultural products from parts of Harford and Baltimore Counties and southern Pennsylvania to the port of Baltimore.

Today the building serves as the American headquarters of SUN Automation Group which makes feeding, printing and converting machinery for corrugated box production.

[6] A notable resident of Glen Arm was Charles Joseph Bonaparte (1851–1921), whose country estate Bella Vista was in the area.

In August, 2019, the Baltimore County Council designated the old Ma & Pa Railroad station, built in 1909, as a protected historical landmark.