Giovanni Marciani (c. 1605 – c. 1663) was an Italian composer, singer, and organist.
Beginning in 1616 He was educated at the Collegium Germanicum et Hungaricum where he was also trained as a singer.
After completing his studies, he worked as a paid tenor at that same institution under Giacomo Carissimi.
He simultaneously worked as a court musician to the Prince of Gallicano from 1645 through 1653; maestro di cappella at the San Giovanni dei Fiorentini (1645–1659); and was the organist at the San Luigi dei Francesi from 1649 through 1653.
He mainly a composer of madrigals, motets, and cantatas; many of which are contained in music anthologies published in Rome between the years 1645 and 1663.