A safety scalpel (1, 80, 90, 100, 110, 120, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 251, 261, 271) comprising: a handle (2, 72, 91, 102, 111, 121, 141, 171, 181, 191, 201, 221, 231, 248, 258, 267, 278, 800); a blade cartridge (3, 60, 92, 101, 112, 122, 142, 163, 172, 182, 192, 202, 222, 232, 247, 257, 263, 277, 802) releasably attached to the handle, the blade cartridge comprising: a blade (6, 64, 82, 107, 114, 124, 131, 143, 268); a housing (7, 61, 96, 109); and a blade holder (8, 62, 81, 98, 108, 113, 123, 130, 149, 233, 246, 256, 266, 276) in communication with the blade, wherein the blade holder is configured to allow the blade to extend between a stowed position in a pre-cutting state of the blade holder and a cutting position upon activation of the blade holder; and a resilient lock member (10, 95, 241, 251, 264, 272) disposed within the housing, wherein the resilient lock member is in an unbiased condition when the blade holder is in the pre-cutting state, and wherein the resilient lock member is configured to engage the blade holder to lock the blade cartridge to the handle when the blade is in the cutting position upon activation of the blade holder, wherein the resilient lock member is arranged to be moved by the blade holder into a locking aperture (11, 23, 106, 265) of the handle to lock the blade cartridge to the handle when the blade is in the cutting position upon activation of the blade holder. a handle (2, 72, 91, 102, 111, 121, 141, 171, 181, 191, 201, 221, 231, 248, 258, 267, 278, 800); a blade cartridge (3, 60, 92, 101, 112, 122, 142, 163, 172, 182, 192, 202, 222, 232, 247, 257, 263, 277, 802) releasably attached to the handle, the blade cartridge comprising: a blade (6, 64, 82, 107, 114, 124, 131, 143, 268); a housing (7, 61, 96, 109); and a blade holder (8, 62, 81, 98, 108, 113, 123, 130, 149, 233, 246, 256, 266, 276) in communication with the blade, wherein the blade holder is configured to allow the blade to extend between a stowed position in a pre-cutting state of the blade holder and a cutting position upon activation of the blade holder; and a resilient lock member (10, 95, 241, 251, 264, 272) disposed within the housing, wherein the resilient lock member is in an unbiased condition when the blade holder is in the pre-cutting state, and wherein the resilient lock member is configured to engage the blade holder to lock the blade cartridge to the handle when the blade is in the cutting position upon activation of the blade holder, wherein the resilient lock member is arranged to be moved by the blade holder into a locking aperture (11, 23, 106, 265) of the handle to lock the blade cartridge to the handle when the blade is in the cutting position upon activation of the blade holder. a blade (6, 64, 82, 107, 114, 124, 131, 143, 268); a housing (7, 61, 96, 109); and a blade holder (8, 62, 81, 98, 108, 113, 123, 130, 149, 233, 246, 256, 266, 276) in communication with the blade, wherein the blade holder is configured to allow the blade to extend between a stowed position in a pre-cutting state of the blade holder and a cutting position upon activation of the blade holder; and a resilient lock member (10, 95, 241, 251, 264, 272) disposed within the housing, wherein the resilient lock member is in an unbiased condition when the blade holder is in the pre-cutting state, and wherein the resilient lock member is configured to engage the blade holder to lock the blade cartridge to the handle when the blade is in the cutting position upon activation of the blade holder, wherein the resilient lock member is arranged to be moved by the blade holder into a locking aperture (11, 23, 106, 265) of the handle to lock the blade cartridge to the handle when the blade is in the cutting position upon activation of the blade holder.