Gisulf I (also Gisulph, Gisolf, Gisulfo, Gisolfo, Gisulphus, or Gisulfus) (May 930 – November or December 977) was the eldest son of Guaimar II, Lombard Prince of Salerno, and his second wife Gaitelgrima.
He was originally under the regency of his mother and Prisco (Priscus), treasurer (comes tesaurarium) and count of the palace (magister palatii).
In Autumn 966, Pope John XIII led a Roman-Tuscan-Spoletan army against Landulf III of Benevento and his brother Pandulf Ironhead, but Gisulf came to his rescue and no battle was given.
In 973, Gisulf was deposed and removed from office by Landulf of Conza and his sons in alliance with Marinus II of Naples and Manso of Amalfi.
Though Gisulf was married to Gemma, he died heirless in late 977 (or perhaps 978) and Pandulf succeeded in Salerno.