The Duffie Oak is a historic Southern live oak in Mobile, Alabama. Being approximately 300 years old, it is considered by scholars to be the oldest living landmark in the city. It was originally known as the Seven Sisters Oak for its number of large limbs. It was later renamed for former mayor of Mobile George A. Duffee, who lived nearby.
The tree has a circumference at breast height (CBH) of , a height of and a limb spread of . It was recognized by the National Arborist Association in 1977. The Alabama Forestry Commission recognized it as a famous and historic tree in 2003.