Fastening and/or connection device (10; 110, 210) for a jewellery and/or costume jewellery item such as, for example, a chain, a bracelet, a pendant or a charm, said item comprising a first free end and a second free end to be joined, said device (10; 110; 210) comprising a first portion (20; 120) suited to be connected to said first free end of said item and a second portion (30; 130) suited to be connected to said second free end of said item, said device (10; 110; 210) comprising: - a main body (40; 140) suited to be interposed between said first portion (20; 120) and said second portion (30; 130); - first connection means (50; 150; 250) suited to place said main body (40; 140) and said first portion (20; 120) in a disengaged operating configuration or in an engaged operating configuration; - second connection means (60; 160) suited to place said main body (40; 140) and said second portion (30; 130) in a disengaged operating configuration or in an engaged operating configuration; wherein, in order to join said free ends (B1, B2) of said item, said first connection means (50; 150; 250) and said second connection means (60; 160) interact in such a way that said main body (40; 140) and said second portion (30; 130) are placed in said engaged operating configuration through said second connection means (60; 160) only once said main body (40; 140) and said first portion (20; 120) have been placed in said engaged operating configuration through said first connection means (50; 150; 250); and wherein, in order to separate said free ends (B1, B2) of said item, said first connection means (50; 150; 250) and said second connection means (60; 160) interact in such a way that said main body (40; 140) and said first portion (20; 120) are placed in said disengaged operating configuration through said first connection means (50; 150; 250) only once said main body (40; 140) and said second portion (30; 130) have been placed in said disengaged operating configuration by said second connection means (60; 160), characterized in that said first connection means (50; 150; 250) comprise at least one holding seat (24; 124; 224) associated with said first portion (20; 120) and a movable element (52; 152) associated with said main body (40; 140), said movable element (52; 152) comprising a holding element (56; 156) suited to engage said at least one holding seat (24; 124; 224) of said first portion (20; 120) in said engaged operating configuration or said first connection means comprise at least one holding element associated with said first portion and a movable element associated with said main body, said movable element comprising at least one seat suited to engage said holding element of said first portion in said engaged operating configuration. - a main body (40; 140) suited to be interposed between said first portion (20; 120) and said second portion (30; 130); - first connection means (50; 150; 250) suited to place said main body (40; 140) and said first portion (20; 120) in a disengaged operating configuration or in an engaged operating configuration; - second connection means (60; 160) suited to place said main body (40; 140) and said second portion (30; 130) in a disengaged operating configuration or in an engaged operating configuration; wherein, in order to join said free ends (B1, B2) of said item, said first connection means (50; 150; 250) and said second connection means (60; 160) interact in such a way that said main body (40; 140) and said second portion (30; 130) are placed in said engaged operating configuration through said second connection means (60; 160) only once said main body (40; 140) and said first portion (20; 120) have been placed in said engaged operating configuration through said first connection means (50; 150; 250); and wherein, in order to separate said free ends (B1, B2) of said item, said first connection means (50; 150; 250) and said second connection means (60; 160) interact in such a way that said main body (40; 140) and said first portion (20; 120) are placed in said disengaged operating configuration through said first connection means (50; 150; 250) only once said main body (40; 140) and said second portion (30; 130) have been placed in said disengaged operating configuration by said second connection means (60; 160), characterized in that said first connection means (50; 150; 250) comprise at least one holding seat (24; 124; 224) associated with said first portion (20; 120) and a movable element (52; 152) associated with said main body (40; 140), said movable element (52; 152) comprising a holding element (56; 156) suited to engage said at least one holding seat (24; 124; 224) of said first portion (20; 120) in said engaged operating configuration or said first connection means comprise at least one holding element associated with said first portion and a movable element associated with said main body, said movable element comprising at least one seat suited to engage said holding element of said first portion in said engaged operating configuration.