Olib (pronounced [ɔ̌lib]; Italian: Ulbo) is a Croatian island in northern Dalmatia, located north-west of Zadar, south-west of Pag, south-east of Lošinj and just east of Silba with an area of 26.14 km.

Greek geographer Strabo mentions a settlement named Aloip, which was inhabited by the Liburnians. During the Roman rule, Aloip was rebuilt in a different location, in the island's south-west.

Croats colonised the island from the mid-7th to the late 8th centuries. Another wave of Croatian inhabitants arrived in the mid to late 15th century, from Vrlika in the Cetinska Krajina region in Split-Dalmatia County, fleeing the Ottoman invasions. The Chakavian dialect of Croatian is spoken on Olib. Residents call themselves Olibljani.

The island has many historic buildings and ruins. Among these are the Assumption of Mary parish church with its collection of antiquities including Glagolitic codices dating back to the 17th century (housed in the treasury of the parish rectory), the stone tower or kula built for protection from pirates, and the ruins of Saint Paul's Church and Monastery which was abandoned in the 13th century.

In addition to the parish church of the Assumption of Mary, Olib has three other churches. Saint Anastasia is situated inside the village cemetery, Saint Nicholas is located on the cove of Porat, and Saint Rocco is close to the port of Samotvorac.

The traditional products of Olib include wine, olive oil, and cheese. Most of the food is consumed locally rather than being sold in the market.

There is no water supply network on Olib so all homes on the island are built with cisterns to capture rainwater. During the summer months, the island receives an additional supply of water carried by ships if needed.

Olib is connected to the mainland by ferry to Zadar via the islands of Silba and Premuda. The journey to the mainland takes approximately two hours on a catamaran and up to three and a half hours by ferry. Cars are forbidden to be used for transport on the island, instead having to be parked in a designated area adjacent to the harbour.

Although the year-round population hovers around only 100, that number is much larger during the summer months, when both descendants of the island's native population as well as international tourists come to visit. According to the 2021 census, the town of Olib has 113 residents and 64 occupied private households.

The island is part of the northern Zadar Archipelago, which has been designated an Important Bird Area (IBA) by BirdLife International because it supports breeding populations of several species of fish-eating seabirds.

• Magaš, Damir; Faričić, Josip (2002). "Problemi suvremene socio-geografske preobrazbe otoka Oliba" [The Problems of the Contemporary Socio-Geographic Transformation of the Olib Island] (PDF). Geoadria (in Croatian). 7 (2): 35–62. doi:10.15291/geoadria.88. Retrieved 28 December 2019.