An automatically retracting safety needle assembly configured to receive a syringe , the assembly having a distal end and a proximal end, the assembly comprising: a housing, comprising an internal housing (IH) , having a base wall situated at the distal end of the IH; a moving sleeve (MOS) , at least partially disposed within the IH, the MOS comprising a flange wall , the MOS being axially movable; a biasing element (BE) , disposed within the IH, the BE being supported between said base wall and said flange wall, the BE is configured to bias the MOS to the proximal direction; said syringe, disposed in and movable axially within the IH, and coupled to the MOS, said syringe is configured to receive a plunger rod ; an activation fork (AF) , partially disposed within the IH, the AF comprising at least one guiding arm , the at least one guiding arm being coupled with the IH and the MOS so as to prevent proximal motion of the MOS when the assembly is in a non-deployment state; and a retraction mechanism (102, 103, 104, 105; 202, 203, 204, 205; 402, 403, 404, 405), configured to automatically retract the syringe upon completion of injection, wherein the assembly is configured to be deployed for injection by advancing the plunger rod and the AF axially in the distal direction with respect to the IH, the plunger rod advancing until the at least one guiding arm of the AF allows proximal movement of the MOS, thereby causing retraction of said syringe, wherein the distal advancement of the plunger rod is substantially constant without an abrupt increase in resistive force to overcome for activating the retraction mechanism, allowing for safe disposal of the assembly. a housing, comprising an internal housing (IH) , having a base wall situated at the distal end of the IH; a moving sleeve (MOS) , at least partially disposed within the IH, the MOS comprising a flange wall , the MOS being axially movable; a biasing element (BE) , disposed within the IH, the BE being supported between said base wall and said flange wall, the BE is configured to bias the MOS to the proximal direction; said syringe, disposed in and movable axially within the IH, and coupled to the MOS, said syringe is configured to receive a plunger rod ; an activation fork (AF) , partially disposed within the IH, the AF comprising at least one guiding arm , the at least one guiding arm being coupled with the IH and the MOS so as to prevent proximal motion of the MOS when the assembly is in a non-deployment state; and a retraction mechanism (102, 103, 104, 105; 202, 203, 204, 205; 402, 403, 404, 405), configured to automatically retract the syringe upon completion of injection, wherein the assembly is configured to be deployed for injection by advancing the plunger rod and the AF axially in the distal direction with respect to the IH, the plunger rod advancing until the at least one guiding arm of the AF allows proximal movement of the MOS, thereby causing retraction of said syringe, wherein the distal advancement of the plunger rod is substantially constant without an abrupt increase in resistive force to overcome for activating the retraction mechanism, allowing for safe disposal of the assembly. <EOS>