We employ the covariance matrix adaptation evolution strategy (CMA-ES) algorithm to design compact and low-loss S-bends on the standard silicon-on-insulator platform. In line with the CMA-ES-based approach, we present experimental results demonstrating insertion losses of 0.041 dB, 0.025 dB, and 0.011 dB for S-bends with sizes of 3.5 µm, 4.5 µm, and 5.5 µm, respectively, which are the lowest insertion losses within the footprint range smaller than approximately 30 µm2. These outcomes underscore the remarkable performance and adaptability of the CMA-ES to design Si photonics devices tailored for high-density photonic integrated circuits.