The Co-cathedral of San Nicolás de Bari is a church in the Spanish city of Alicante. It is one of the two cathedral seats of the diocese of Orihuela-Alicante, along with the cathedral of El Salvador de Orihuela. It is located in the Abad Penalva square.

It was built on the remains of a mosque and the existence of a chapel is known as early as the 13th century, as it was witness to the meeting of James I of Aragon with the bishop of Barcelona, Arnau de Gurb, and ecclesiastical personalities from Alicante in 1265, when Alicante was part of Castile and King Alfonso X the Wise, to prepare for the conquest of Murcia and suppress the Muslim insurrection. When this new parish church was built in the Christian quarter of Alicante, it was known as the church of Novella de Fora (New Outside) as opposed to Santa María.

Built in the Herrerian Renaissance style, sober on the outside, its current construction was carried out between 1616 and 1662, although its cloister, which is older, dates from the 15th century and was originally built in the Gothic style. The former collegiate church was elevated to the rank of co-cathedral in 1959, and since then has shared the cathedral seat with the Santa Iglesia Catedral del Salvador de Orihuela.

The church has an exterior appearance of great sobriety, which stylistically falls between late Renaissance and early Baroque style. Built according to plans by Agustín Bernardino, a disciple of Juan de Herrera, it nevertheless conserves traces of the cloister from the 15th century, evidence of an earlier, smaller temple that was built on the site of an old mosque.

Saint Nicholas is the patron saint of the city of Alicante, so on 6 December a solemn mass is held in his honour in the Co-cathedral (usually at 11am), followed by a procession through the streets of the city, with a living Saint Nicholas on horseback, passing by the traditional Christmas market.