Yambol (Bulgarian: Ямбол) is a city in southeastern Bulgaria, the administrative centre of Yambol Province. It lies on both banks of the Tundzha in the historical region of Thrace. Today, the town has 85,966 inhabitants as of 2006[update]. It is occasionally spelt 'Jambol'.

The surrounding area has been inhabited since the Neolithic and was the location of the Thracian royal city of Cabyle (later conquered by Philip II of Macedon and the Romans, but destroyed by the Avars in 583). What is today Yambol was founded by Roman Emperor Diocletian in A.D. 293; though it was named Diospolis ('city of Zeus'), the name also reflected the emperor's name. The name later evolved through Diampolis, Hiambouli (in Byzantine chronicles), Dinibouli (Arabic chronicles), Dbilin (in Bulgarian inscriptions), and Diamboli to become Yambol. There is a trend today to reflect its original connections by calling it Yamboli, but that remains unofficial.