Ballestilla Reef (Bulgarian: риф Балестиля, romanized: rif Ballestilla, IPA: [ˈrif bɐlɛˈstilʲɐ]) is the 160 m long in southeast-northwest direction and 40 m wide flat and rocky low-tide elevation off the northwest coast of Snow Island in the South Shetland Islands, Antarctica. Its surface area is 0.38 ha. The vicinity was visited by early 19th century sealers. The feature is named after the geodetic instrument ballestilla, also known as Jacob's staff or cross-staff; in association with other names in the area deriving from the early development or use of geodetic instruments and methods.