In Roman mythology, Fortuna (Greek equivalent Tyche) was the personification of luck, hopefully of good luck. She also had the name Annonaria. Under this name, she protected grain supplies. Fortuna had a retinue that included Copia among her blessings.

Fortuna was propitiated by mothers. Traditionally her cult was introduced to Rome by Servius Tullius.

Fortuna had a temple in the Forum Boarium, a public sanctuary on the Quirinalis, as the tutelary genius of Roma herself (Fortuna Populi Romani the 'Fortune of the Roman people'), and an oracle in Praeneste where the future was chosen by a small boy choosing oak rods with possible futures written on them.

In art, she was portrayed standing in an expensive dress; she was associated with the cornucopia, rudder, ball and blindfold, and the wheel.

All over the Roman world, Fortuna was worshipped at a great number of shrines under various titles that were applied to her according to the various circumstances of life in which her influence was hoped to have a positive effect. Fortuna was not always positive: she was doubtful (Fortuna Dubia); she could be 'fickle fortune' (Fortuna Brevis), or downright evil luck (Fortuna Mala).

Aspects of Fortuna

• Fortuna Annonaria brought the luck of the harvest
• Fortuna Primigenia directed the fortune of a newborn child at the moment of birth
• Fortuna Virilis attended a man's career
• Fortuna Redux brought one safely home
• Fortuna Respiciens
• Fortuna Muliebris the luck of a woman. Typical of Roman attitudes, the fortune of a woman in marriage, however, was Fortuna Virilis.
• Fortuna Victrix brought victory in battle

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Fortuna is also the name of a cryptographically secure pseudo-random number generator design by Neils Ferguson and Bruce Schneier. They claim it to be an improvement over their prior design, Yarrow.