Merchandise anti-theft device which is configured to be attached to merchandise to be protected, in particular textile products, comprising: - a housing, and - a locking mechanism (110, 110a; 110b)which is at least partially accommodated in the housing and comprises a securing element (112, 112a; 112b), said securing element being adjustable between a securing position in which it engages with the merchandise to be protected and a release position in which the merchandise anti-theft device can be released and removed from the merchandise to be protected, wherein the locking mechanism (110, 110a; 110b) further comprises - a wire (130a; 130b) formed at least partially from a shape-memory alloy and - a guide element (120a; 120b) which can be brought into a releasable engagement connection with the securing element (112, 112a; 112b) and has a first position in which movement of the securing element from the securing position to the release position is prevented, and a second position in which movement of the securing element from the securing position to the release position is permitted, characterized in that both ends (132a, 134a; 132b, 134b) of the wire (130a; 130b) are fixed immovably relative to the housing and a contact portion (136a; 136b) of the wire located between these two ends is in contact with the guide element (120a; 120b) or a part connected to it in such a way that, if the wire (130a; 130b) becomes shorter, the guide element (120a; 120b) is transferred from the first position to the second position. - a housing, and - a locking mechanism (110, 110a; 110b)which is at least partially accommodated in the housing and comprises a securing element (112, 112a; 112b), said securing element being adjustable between a securing position in which it engages with the merchandise to be protected and a release position in which the merchandise anti-theft device can be released and removed from the merchandise to be protected, the locking mechanism (110, 110a; 110b) further comprises - a wire (130a; 130b) formed at least partially from a shape-memory alloy and - a guide element (120a; 120b) which can be brought into a releasable engagement connection with the securing element (112, 112a; 112b) and has a first position in which movement of the securing element from the securing position to the release position is prevented, and a second position in which movement of the securing element from the securing position to the release position is permitted, - a wire (130a; 130b) formed at least partially from a shape-memory alloy and - a guide element (120a; 120b) which can be brought into a releasable engagement connection with the securing element (112, 112a; 112b) and has a first position in which movement of the securing element from the securing position to the release position is prevented, and a second position in which movement of the securing element from the securing position to the release position is permitted, characterized in that both ends (132a, 134a; 132b, 134b) of the wire (130a; 130b) are fixed immovably relative to the housing and a contact portion (136a; 136b) of the wire located between these two ends is in contact with the guide element (120a; 120b) or a part connected to it in such a way that, if the wire (130a; 130b) becomes shorter, the guide element (120a; 120b) is transferred from the first position to the second position.