Saint Nino (sometimes St. Nune, St. Nina or St. Ninny; Georgian: წმინდა ნინო, romanized: ts'minda nino; Armenian: Սուրբ Նունե, romanized: Surb Nune; Greek: Ἁγία Νίνα, romanized: Hagía Nína) was a woman who preached Christianity in the territory of the Kingdom of Iberia in what is now Georgia. Her preaching led to the Christianization of Iberia.

According to most traditional accounts, she belonged to a Greek-speaking Roman family from Kolastra, Cappadocia, was a relative of Saint George, and came to Iberia from Armenia.

At the age of 14, Nino served as a lady-in-waiting to a Christian noblewoman whom Diocletian wished to marry. The woman refused, and Nino, together with her mistress and other attendants, fled to avoid persecution. All were killed except Nino, who survived by hiding. According to tradition, she then received a vision of the Virgin Mary, who gave her a grapevine cross and instructed her to travel to Iberia (modern-day Georgia) to spread the Christian faith. Nino traveled to Iberia, preached Christianity, and converted the entire country.

According to tradition, she performed miraculous healings and converted the Georgian queen, Nana, and eventually the pagan king Mirian III of Iberia, who, lost in darkness and blinded on a hunting trip, found his way only after praying to "Nino's God". Mirian declared Christianity the official religion of his kingdom (c. 326), and Nino continued her missionary activities among Georgians until her death.

Her tomb is still venerated at the Bodbe Monastery in Kakheti, eastern Georgia. She has become one of the most venerated saints of the Georgian Orthodox Church, and her attribute, the grapevine cross, is a symbol of Georgian Christianity.

She was named Christiana by Rufinus and Theognosta by the Byzantines.

The oldest extant source describing the life of Saint Nino is the Latin account by Rufinus in his Historia ecclesiastica, composed around 403. This account is based on oral information provided to Rufinus by a Georgian prince named Bacurius, whom he met in Palestine. Bacurius was a member of the royal house of Iberia and recounted events that had taken place just over half a century earlier, during the lifetime of his parents or, at the latest, his grandparents. Scholars have hypothesized that Rufinus also relied on the Ecclesiastical History of Gelasius of Caesarea, a Greek-language work that is now lost. Other early Christian authors who wrote about Saint Nino include Socrates of Constantinople, Sozomen, Theodoret of Cyrrhus, Gelasius of Cyzicus, Movses Khorenatsi and Theophanes the Confessor. The 10th-century Georgian hagiographic work Conversion of Kartli largely repeats the accounts of earlier authors. The only notable difference is that, while earlier sources report that Nino was captured by the Iberians, the Conversion of Kartli does not mention this.

Saint Nino’s ethnic background is not clearly known. She was born in Cappadocia, a region inhabited by many ethnic groups, and it is certain that she spoke Greek and Hebrew. At the beginning of her stay in Kartli, she communicated with the Georgians through members of the local Jewish community and required a Greek interpreter to communicate with the king's messenger.