The Sinjska alka is an equestrian competition held in the Croatian town of Sinj every first Sunday in August since 1715.

The Sinjska alka [siɲska alka] is an equestrian competition held in the Croatian town of Sinj every first Sunday in August since 1715. It commemorates a Croatian-Venetian victory over Ottomans on August 14, 1715 in which the local Christian population of around 700 Croats in cooperation with a smaller number of Venetians managed to defend Sinj against 60,000 Ottoman soldiers led by Mehmed-paša Ćelić. Because of this victory, the Venetians retained control over Sinj and integrated it into the Venetian Dalmatia, according to the terms of the Treaty of Passarowitz signed in 1718. The people of Sinj believe that the Lady of Sinj miraculously drove away Ottomans, thus helping them to defend their town. On the national holiday of the Assumption of Mary (Velika Gospa) on August 15, in honor of Lady of Sinj, a procession is organised, during which horsemen in full regalia ("Alkari") parade a painting of Our Lady of Sinj throughout the town streets.

The Alka itself is an equestrian competition in which various horsemen riding at full gallop aim their lances at a hanging metal ring (alka), and are awarded points according to which sector of the ring they are able to pierce.