A protective helmet comprising: an outer shell configured for surrounding a head of a user; at least one accessory attachment rail connected to the outer shell, the accessory attachment rail comprising: a body having a front end, a rear end, and two or more slots (208, 208a, 208b) between the front end and the rear end, each of the two or more slots (208, 208a, 208b) configured for removably receiving at least one helmet accessory; a locking mechanism associated with each of the two or more slots (208, 208a, 208b) for automatically locking the at least one helmet accessory in at least one of the two or more slots (208, 208a, 208b) upon insertion of the at least one helmet accessory within at least one of the two or more slots (208, 208a, 208b) and for preventing removal of the at least one helmet accessory from within the at least one of the two or more slots (208, 208a, 208b) until the locking mechanism is unlocked; and at least one connection element for connecting the accessory attachment rail to the outer shell; wherein each of the two or more slots (208, 208a, 208b) has an open end configured for removably receiving the at least one helmet accessory, a closed end opposite the open end, and a channel having a perimeter wall between the open end and the closed end. an outer shell configured for surrounding a head of a user; at least one accessory attachment rail connected to the outer shell, the accessory attachment rail comprising: a body having a front end, a rear end, and two or more slots (208, 208a, 208b) between the front end and the rear end, each of the two or more slots (208, 208a, 208b) configured for removably receiving at least one helmet accessory; a locking mechanism associated with each of the two or more slots (208, 208a, 208b) for automatically locking the at least one helmet accessory in at least one of the two or more slots (208, 208a, 208b) upon insertion of the at least one helmet accessory within at least one of the two or more slots (208, 208a, 208b) and for preventing removal of the at least one helmet accessory from within the at least one of the two or more slots (208, 208a, 208b) until the locking mechanism is unlocked; and at least one connection element for connecting the accessory attachment rail to the outer shell; wherein each of the two or more slots (208, 208a, 208b) has an open end configured for removably receiving the at least one helmet accessory, a closed end opposite the open end, and a channel having a perimeter wall between the open end and the closed end. a body having a front end, a rear end, and two or more slots (208, 208a, 208b) between the front end and the rear end, each of the two or more slots (208, 208a, 208b) configured for removably receiving at least one helmet accessory; a locking mechanism associated with each of the two or more slots (208, 208a, 208b) for automatically locking the at least one helmet accessory in at least one of the two or more slots (208, 208a, 208b) upon insertion of the at least one helmet accessory within at least one of the two or more slots (208, 208a, 208b) and for preventing removal of the at least one helmet accessory from within the at least one of the two or more slots (208, 208a, 208b) until the locking mechanism is unlocked; and at least one connection element for connecting the accessory attachment rail to the outer shell; wherein each of the two or more slots (208, 208a, 208b) has an open end configured for removably receiving the at least one helmet accessory, a closed end opposite the open end, and a channel having a perimeter wall between the open end and the closed end.