Understanding biological systems and mimicking their functions require electronic tools that can interact with biological tissues with matched softness. Conductive materials that match the softness of biological tissue are thus highly demanded for the construction of ultrasoft electronics. However, the commonly employed intrinsically stretchable materials usually contain solvents that limit stability for long-term use or possess low electronic conductivity. Additionally, integrating such ultrasoft and conductive materials into electronic devices is poorly explored. This article reports a solvent-free, ultrasoft and conductive PDMS bottlebrush elastomer composite with single-wall carbon nanotubes as conductive fillers. The conductive SWCNT/BBE with a filler concentration of 0.4−0.6 wt % reveals an ultralow Young’s modulus (<11 kPa) and satisfactory conductivity (>2 S/m) as well as strong wet-adhesion property. Furthermore, we fabricate ultrasoft electronics based on laser cutting and 3D printing of conductive and non-conductive BBEs and demonstrate their potential applications in wearable sensing, soft robotics, and electrophysiological recording.