There is described a quick-coupling pipe fitting, comprising a female element (1) and a male element (2) that can be coupled together, formed by fixed parts (4, 6, 9; 29, 32) and by axially slidable parts (10, 15; 37, 44) that, when at rest, arrange themselves in a position wherein they close the passage of the fluid and, when the two elements (1, 2) are coupled together, they are displaced from engagement with corresponding parts of the other element in a position wherein the abovementioned passage is open. Said male (2) and female (1) elements can be coupled together by means of screw-based connecting means and their said parts have coplanar surfaces (28, 50) at mutually connectable ends.