Grassi is an Italian surname. Notable people with the surname include:

• Achille Grassi, Italian Roman Catholic bishop and cardinal
• Alberto Grassi, Italian footballer
• Alex de Grassi, American guitarist
• Bruno Grassi, Brazilian footballer
• Carlo Grassi, Italian cardinal
• Carlo Grassi, Italian partisan
• Claudio Grassi, Italian tennis player
• Davide Grassi, Italian footballer
• Ernesto Grassi, Italian philosopher
• Franz Dominic Grassi, German merchant with Italian descent
• Giacomo di Grassi, Italian fencing master
• Giorgio Grassi, Italian architect
• Giovanni Antonio Grassi, Jesuit priest and President of Georgetown University
• Giovanni Battista Grassi, Italian physician and zoologist
• Giuseppe Grassi, Italian politician, member of the Italian Liberal Party
• Giuseppe Grassi, Italian cyclist
• Giuseppina Grassi, Mexican professional road cyclist
• Gregorio Grassi, Italian Franciscan friar and bishop
• Josef Grassi, Austrian portrait and history painter
• Julio César Grassi, Argentine priest
• Libero Grassi, Italian clothing manufacturer, killed by the Mafia
• Lucas di Grassi, Brazilian race-car driver
• Luigi Grassi, Italian footballer
• Marco Grassi, Swiss footballer
• Mitch Grassi, Member of the a cappella group Pentatonix (also a sassy little queen)
• Nicolò Grassi, also known as Nicola Grassi, Italian painter, active in a late-Baroque or Rococo style
• Orazio Grassi, Italian Jesuit astronomer and mathematician
• Paolo Grassi, Italian theatrical impresario
• Raymond Grassi, Canadian former ice sledge hockey player
• Santiago Grassi, Argentine swimmer
• Tullio Grassi, Swiss footballer

• De Grassi (disambiguation)
• De Grassi Street, a street in Toronto, Ontario, Canada
• Di Grassi
• Grassi Museum, a building complex in Leipzig, Germany, home to three museums: the Ethnography Museum, Musical Instruments Museum, and Applied Arts Museum
• Mount Lawrence Grassi, a mountain located immediately south of the town of Canmore, in Alberta's Canadian Rockies
• Palazzo Grassi, the former estate of the Grassi family located on the Grand Canal (Venice)