Highly stretchable and conductive composites have gained tremendous research interests due to the imperative demands in the fields of stretchable electronics and soft robotics. However, it is challenging to maintain the original performance of the composites under complex external deformations. Here, a one‐step dual‐material 3D printing technique is developed to rationally assemble liquid metal (LM) into an elastomer lattice. The 3D interconnected and deformable liquid conductive network is supported by a highly ordered and robust polydimethylsiloxane lattice skeleton, yielding the resultant composites high electrical conductivity (1.98 × 106 S m−1), stretchability (180%), and electromagnetic interference (EMI) shielding effectiveness (72 dB). Unlike those composites with dispersed fillers, the LM/elastomer lattice composites deliver negligible electromechanical coupling, showing a negative resistance change of only −2% at a large tensile strain of 100%. The composites also exhibit strain‐invariant EMI shielding performance in a strain range of 0–100%, and present exceptional stability over 1000 rigorous cycles of stretching and releasing. The applications of the composites in flexible display circuits, microwave shielding layer, and EMI shields in wireless power transmission systems are demonstrated. The current findings suggest an effective strategy for fabricating LM‐based composites with precisely controlled and unprecedented multi‐functionality.