Defender Alim Ozturk has become Sunderland's first signing of the summer.
He will join the Black Cats on July 1 in a two-year deal after he left Turkish side Boluspor.
The centre-back is a former Turkish under 21 international who was born in the Netherlands.
He began his career at Dutch side SC Cambuur, before moving to Trabzonspor. The 25-year-old then made the move to Scottish side Heart of Midlothian, spending three years at the club, during which time he became its captain.
He returned to Turkish football in January 2017, signing an eighteen-month deal with Boluspor.
Manager Jack Ross said: