A device (1) for the automatic injection of a product (3) at an injection site (4), the product (3) being transported by a container (50) having an open proximal end and a substantially closed distal end and which it has a defined reservoir between them, and a needle (6) disposed at the distal end and in fluid communication with the reservoir to provide an outlet port for the product (3) of the container, and a piston (7) provided in the container and that can be moved with respect to the container, causing the movement of the piston that the product is ejected from the container through the needle, said device comprising: - a housing (8), which has a generally cylindrical shape, for the container , the container being able to move relative to said housing between an initial position, in which a needle tip does not extend beyond a distal end of said housing and in which the container is in one of a passive state and an active state, to an insertion position, separated distally with respect to said initial position and in which the tip of the needle extends beyond said distal end of said housing, preventing movement of the container out of its initial position when the container is in its passive state, and allowing itself when the container is in its active state, and - a safety protection (10) coupled to said housing (8) for its movement between a first position and a second position in which the tip of the needle does not extend beyond a distal end of said security protection, placing the movement of said security protection (10) out of its first position the container (50) in its active state , said safety protection (10) being able to move to its second position when the container (50) is in said insertion position, said safety protection (10) being secured against the proximal movement when in said second position, - a needle guard (2) coupled to a non-protective member (15) that is coupled with said housing (8) and covering the needle (6) before the use of sai
