Roberto Longo (born 9 May 1953) is an Italian mathematician, specializing in operator algebras and quantum field theory.

[5] Roberto Longo is known in particular for his work with Sergio Doplicher on split inclusions of von Neumann algebras[6] and for having solved, independently with Sorin Popa, the Stone-Weierstrass conjecture for factorial states.

[9] In a work with Yasuyuki Kawahigashi, Longo classified the discrete series of conformal chiral networks of von Neumann algebras.

[10] Together with Vincenzo Morinelli and Karl-Henning Rehren, he also showed that particles with infinite spin cannot appear in a local theory.

[28] In 2018 he was member of the sectional panel Mathematical Physics of the International Congress of Mathematicians in Rio de Janeiro.