Highly stretchable, soft silicone elastomers are of great interest for the fabrication of stretchable, soft devices. However, there is a lack of available chemistries capable of efficiently preparing silicone elastomers with superior stretchability and softness. Here we show an easy curing reaction to prepare silicone elastomers, in which a platinum-catalyzed reaction of telechelic/multi-hydrosilane (Si-H) functional polydimethylsiloxane (PDMS) in the presence of oxygen and water leads to slow crosslinking. This curing chemistry allows versatile tailoring of elastomer properties, which exceed their intrinsic limitations. Specifically, both highly stretchable silicone elastomers (maximum strain of 2800%) and extremely soft silicone elastomers (lowest shear modulus of 1.2 kPa) are prepared by creating highly entangled elastomers and bottle-brush elastomers from commercial precursor polymers, respectively.