Abstract: Photoacids are molecules which become (more) acidic under photo-irradiation, and they find valuable applications in organic synthesis and biological chemistry. We herein report a new photoacid, HDMAPAN-(BF4)2, which functions by a different photoacidity mechanism than existing ones. HDMAPAN-(BF4)2, consisting of one dibenzotropylium and one anilinium moieties connected together by a biaryl C-C bond, shows an exceptionally low computed 𝑝𝐾 𝑎 ℎ𝑣 (-12.3), which is within the range of superphotoacids. Surprisingly, despite the electronic S0 → S1 transition being located in the dibenzotropylium unit, the photo-excitation affects the acidity of the proton on the anilinium unit. Our computational investigations using TD-DFT reveal that