Singlet oxygen sensitized photodynamic therapy (PDT) relies on the concentration of oxygen in the tissue to be treated. Most cancer lesions, however, have poor vasculature and, as a result, are hypoxic, significantly hindering PDT efficacies. An oxygen-independent PDT method may circumvent this limitation. To address this, we prepared sulfonium salts that produced a pH drop within HCT 116 cells via the generation of a photoacid within the cytosol. This process was driven by one- or two-photon absorption (1PA or 2PA) of the endocytosed photoacid generators (PAGs). One of these PAGs, which had a significantly lower dark cytotoxicity and was more efficient in generating a photoacid, effectively induced necrotic cell death in the HCT 116 cells. The data suggest that PAGs may be an attractive alternative PDT modality to selectively induce cell death in oxygen-deprived tissue such as tumors.