Greenhouse (11) with natural ventilation comprising a supporting structure (13) of a covering mantle (15), said structure and mantle defining, as a whole, a tunnel-shaped body (17) which delimits a room (19) inside the greenhouse and is adapted to be fixed to the ground, and a ventilation chamber (23) which is adapted to be passed through by air flows coming from the greenhouse inner room and directed to the outside and vice versa and extends longitudinally inside the tunnel and is separated from the outer environment by at least one waterproof portion (25) of the mantle (15) and by at least one anti-insect net (27) which is adjacent to the at least one waterproof portion (25) of the mantle and through which the chamber (23) communicates with the outer environment, said chamber communicating with the inner room (19) through at least one lateral opening (29) provided between the waterproof portion (25) of the mantle and at least one water-draining surface (31) delimiting downwards the chamber (23) and separating it from the inner room (19).
