Self-cleaning filter for pressure vessels, particularly for liquefied gas containers, characterized in that it comprises: - a filter chamber communicating with a pipe for the passage of liquefied gas and with the inside of the container through first and second ports, - a tubular cylindrical filter element mounted in said chamber and having one axial end closed by a base and an axially opposed open end, wherein the shell of said filter element forms a first filter surface for retaining the smallest impurities during the delivery of gas from the container, said first filter surface being positioned in said chamber and being such that the gas delivered from the container through the said chamber and directed towards said pipe passes through said filter surface after flowing over the walls of the said chamber, wherein the edge of said open end forms a plug, - a valve seat formed in the first port, wherein said plug in combination with said valve seat creates by-pass valve means for by-passing the first filter surface, for bringing liquefied gas from the pipe into the container during the filling of the latter, without passing the gas through the first filter surface, - a spring acting between a pre-filter mounted in the second port and the filter element to press the plug against the seat in order to shut the latter off; whereby, when said by-pass valve means are shut off, the gas delivered into the container to the chamber is forced to pass through the filter surface, while, when during the filling of the container said by-pass valve means are open in said chamber, they allow for by-passing the first filter surface and bringing liquefied gas from the pipe into the filter chamber, in such a way that the liquefied gas brought in to fill the container through said by-pass valve means causes flushing of the walls of said chamber and of said first filter surface, and - retaining means in said chamber for temporarily retaining suspended impurities in the liquefied gas against the walls of said chamber during delivery, and for releasing them when flushing takes place during the filling of the container. - a filter chamber communicating with a pipe for the passage of liquefied gas and with the inside of the container through first and second ports, - a tubular cylindrical filter element mounted in said chamber and having one axial end closed by a base and an axially opposed open end, wherein the shell of said filter element forms a first filter surface for retaining the smallest impurities during the delivery of gas from the container, said first filter surface being positioned in said chamber and being such that the gas delivered from the container through the said chamber and directed towards said pipe passes through said filter surface after flowing over the walls of the said chamber, wherein the edge of said open end forms a plug, - a valve seat formed in the first port, wherein said plug in combination with said valve seat creates by-pass valve means for by-passing the first filter surface, for bringing liquefied gas from the pipe into the container during the filling of the latter, without passing the gas through the first filter surface, - a spring acting between a pre-filter mounted in the second port and the filter element to press the plug against the seat in order to shut the latter off; whereby, when said by-pass valve means are shut off, the gas delivered into the container to the chamber is forced to pass through the filter surface, while, when during the filling of the container said by-pass valve means are open in said chamber, they allow for by-passing the first filter surface and bringing liquefied gas from the pipe into the filter chamber, in such a way that the liquefied gas brought in to fill the container through said by-pass valve means causes flushing of the walls of said chamber and of said first filter surface, and - retaining means in said chamber for temporarily retaining suspended impurities in the liquefied gas against the walls of said chamber during delivery, and for releasing them when flushing takes place during the filling of the container.