A needle assembly for use with a container, comprising: i) a needle hub having a needle fixed thereon, said needle having a distal tip, and ii) a needle safety system comprising: - a protective ring capable of moving in translation with respect to said needle hub between a distal position, in which said protective ring surrounds at least the distal tip of said needle and in which said needle assembly is in one of a storage condition or end-of-use condition, and a proximal position, in which said protective ring leaves said distal tip uncovered and wherein said needle assembly is in a use condition, said protective ring being movable in said proximal position between intermediate positions in which the needle is partially inserted into an injection site and a most proximal position, in which the needle is fully inserted into said injection site, - foldable means (40, 43, 47, 48) coupled to said protective ring and to said needle hub, capable of going from an unfolded configuration, in which said protective ring is in its distal position, to a fully folded configuration, in which said protective ring is in its most proximal position, - biasing means capable of expanding from a stressed state to a rest state urging said foldable means from their fully folded configuration to their unfolded configuration when the needle is removed from the injection site, - retaining means (22, 14) for maintaining said biasing means in an intermediate stressed state at least in the storage condition of the needle assembly, - deactivating means (47a, 20b) for releasing said retaining means during the insertion step of the needle, locking means (20b, 21, 47b, 47c) for maintaining said foldable means in their unfolded configuration in the end-of-use condition of said needle assembly, characterised in that said safety system comprises at least a mobile ring, coupled to said needle hub by said biasing means, said mobile ring being movable in translation with respect to said needle hub between a proximal position, in which said mobile ring is limitedly mobile in translation and in rotation with respect to said needle hub and forms at least part of said retaining means and deactivating means, and a distal position, in which said mobile ring forms at least part of said locking means. i) a needle hub having a needle fixed thereon, said needle having a distal tip, and ii) a needle safety system comprising: - a protective ring capable of moving in translation with respect to said needle hub between a distal position, in which said protective ring surrounds at least the distal tip of said needle and in which said needle assembly is in one of a storage condition or end-of-use condition, and a proximal position, in which said protective ring leaves said distal tip uncovered and wherein said needle assembly is in a use condition, said protective ring being movable in said proximal position between intermediate positions in which the needle is partially inserted into an injection site and a most proximal position, in which the needle is fully inserted into said injection site, - foldable means (40, 43, 47, 48) coupled to said protective ring and to said needle hub, capable of going from an unfolded configuration, in which said protective ring is in its distal position, to a fully folded configuration, in which said protective ring is in its most proximal position, - biasing means capable of expanding from a stressed state to a rest state urging said foldable means from their fully folded configuration to their unfolded configuration when the needle is removed from the injection site, - retaining means (22, 14) for maintaining said biasing means in an intermediate stressed state at least in the storage condition of the needle assembly, - deactivating means (47a, 20b) for releasing said retaining means during the insertion step of the needle, - a protective ring capable of moving in translation with respect to said needle hub between a distal position, in which said protective ring surrounds at least the distal tip of said needle and in which said needle assembly is in one of a storage condition or end-of-use condition, and a proximal position, in which said protective ring leaves said distal tip uncovered and wherein said needle assembly is in a use condition, said protective ring being movable in said proximal position between intermediate positions in which the needle is partially inserted into an injection site and a most proximal position, in which the needle is fully inserted into said injection site, - foldable means (40, 43, 47, 48) coupled to said protective ring and to said needle hub, capable of going from an unfolded configuration, in which said protective ring is in its distal position, to a fully folded configuration, in which said protective ring is in its most proximal position, - biasing means capable of expanding from a stressed state to a rest state urging said foldable means from their fully folded configuration to their unfolded configuration when the needle is removed from the injection site, - retaining means (22, 14) for maintaining said biasing means in an intermediate stressed state at least in the storage condition of the needle assembly, - deactivating means (47a, 20b) for releasing said retaining means during the insertion step of the needle,