Fitting for connecting pipes, in particular at least one flexible pipe, comprising: - at least one first tubular element provided, at one end thereof, with a first inlet/outlet opening and at its interior defining a first duct; - at least one second tubular element provided, at one end thereof, with a second inlet/outlet opening and at its interior defining a second duct, said first and second tubular elements being connected to each other at respective opposite ends to the respective inlet/outlet opening, in a manner such that said first and second ducts are in communication with each other and overall define a joint duct of the fitting placing said first inlet/outlet opening and said second inlet/outlet opening in fluid communication, wherein at least said first tubular element is provided with at least one through opening, between an external surface of the first tubular element and an internal surface of the first tubular element, said internal surface being directed towards, and defining, said first duct, said through opening defining a respective empty space between the external surface and the internal surface of the first tubular element, the fitting being configured for operating at least in an insertion condition, in which it allows a pipe to be fit around said first tubular element, and a clamping condition, in which the pipe is pressed and stably locked on the first tubular element, said fitting being characterized in that, in said clamping condition, said empty space defined by said at least one through opening is configured for being at least partially occupied by a portion of said pipe pressed on the first tubular element. - at least one first tubular element provided, at one end thereof, with a first inlet/outlet opening and at its interior defining a first duct; - at least one second tubular element provided, at one end thereof, with a second inlet/outlet opening and at its interior defining a second duct, said first and second tubular elements being connected to each other at respective opposite ends to the respective inlet/outlet opening, in a manner such that said first and second ducts are in communication with each other and overall define a joint duct of the fitting placing said first inlet/outlet opening and said second inlet/outlet opening in fluid communication, wherein at least said first tubular element is provided with at least one through opening, between an external surface of the first tubular element and an internal surface of the first tubular element, said internal surface being directed towards, and defining, said first duct, said through opening defining a respective empty space between the external surface and the internal surface of the first tubular element, the fitting being configured for operating at least in an insertion condition, in which it allows a pipe to be fit around said first tubular element, and a clamping condition, in which the pipe is pressed and stably locked on the first tubular element, said fitting being characterized in that, in said clamping condition, said empty space defined by said at least one through opening is configured for being at least partially occupied by a portion of said pipe pressed on the first tubular element.