We report results from searches for new physics with low-energy electronic recoil data recorded with the XENON1T detector. With an exposure of 1042 kg x  226.9 days and an unprecedented low background rate of (76 ±2) events/(tonne x year x keV) between 1-30 keV, the data enables the most sensitive searches for new physics such as solar axions, an enhanced neutrino magnetic moment using solar neutrinos, and bosonic dark matter.