Karen Ann Martin (December 18, 1960 - September 11, 2001) was the purser on American Airlines Flight 11 on September 11, 2001, that was hijacked and crashed into the North Tower of the World Trade Center as part of the September 11 attacks.

Karen lived in Danvers, Massachusetts, and became a flight attendant for American Airlines in 1989.

On September 11, 2001, Karen was working the morning shift as the head flight attendant in the first class cabin on American Airlines Flight 11. As she and the flight attendants were preparing for cabin service, the al-Shehri brothers walked up to her and Bobbi Arestegui and stabbed them.