Many artists worked on the Trevi Fountain, I am only going to cover the main three.

Pietro da Cortona was a practitioner of the High Baroque style. Born in Cortona, he studied in Florence and then Rome, learning to paint primarily by teaching himself. Painter, architect, and sculpture designer, the energetic Pietro always worked simultaneously on architectural and decorative projects. His combination of paint and stucco became Europe's official decorative style for aristocratic dwellings.

Bernini was a sculptor, painter and architect and a formative influence as an outstanding exponent of the Italian Baroque.  He originally worked in the Late Mannerist tradition but rejected the contrived tendencies of this style.  A succession of powerful patrons in Rome and in Paris assured his reputation as an entrepreneurial artist who captured the spirit of the Counter-Reformation. His extreme and intense characterizations have fallen in and out of favor but his Baroque legacy remains intact.

Niccolo Salvi was an Italian architect whose designs combined late Baroque with a classical feeling for composition.  Salvi won a commission for the fountain. He based it in part on a plan by 17th-century Italian architect Cortona.  Salvi's design for the Trevi Fountain joins elements of architecture, sculpture, and landscape.