Gioacchino Conti (28 February 1714 – 25 October 1761), best known as Gizziello, was an Italian soprano castrato opera singer.
Conti was born in Arpino. After studying in Naples with Domenico Gizzi, whom he would later be dubbed after, he made his debut in Rome at a young age, in Leonardo Vinci's Artaserse (1730).
His career led him throughout Europe and especially to London, where he was engaged by Händel, with whom he would build up profitable collaboration relations. Conti performed in many of his works, such as Atalanta, Giustino, Berenice and Arminio, as well as in a revival of Ariodante.
He executed later many first performances for the best famed musicians of his time, including Niccolò Jommelli (Manlio, 1746), Baldassare Galuppi (Artaserse, 1751) and Johann Adolf Hasse (Demetrio, 1747).
After 1759 Conti left the stage and settled in Rome, where he spent the last two years of his life.
Being a very sharp sopranist for his time (Händel got him to repeatedly reach up to C6), Conti was not quite well disposed towards abuse of coloratura and he chose rather to turn to better account his fluent and smooth style of rendering and expression: he has thus remained famous as a sentimental and gentle singer, but he also always kept, of course, a condition of absolute excellence at vocal virtuosity, even though not so acrobatic as, for instance, that of his contemporary (and friend) Farinelli.