Photoelectron spectra of the MX2- (M = Li, Na; X = Cl, Br, I) superhalogen anions have been obtained for the first time. The first vertical detachment energies (VDEs) were measured to be 5.92+/-0.04 (LiCl2-), 5.86+/-0.06 (NaCl2-), 5.42+/-0.03 (LiBr2-), 5.36+/-0.06 (NaBr2-), 4.88+/-0.03 (LiI2-), and 4.84+/-0.06 eV (NaI2-), which are all well above the 3.61 eV electron detachment energy of Cl-, the highest among atomic anions. Experimental photoelectron spectra have been assigned on the basis of ab initio outer valence Green function (OVGF) calculations. The corresponding theoretical first VDEs were found to be 5.90 (LiCl2-), 5.81 (NaCl2-), 5.48 (LiBr2-), 5.43 (NaBr2-), 4.57 (LiI2-), and 4.50 eV (NaI2-), in excellent agreement with the experimental values. Photodetachment from the top four valence molecular orbitals (2 sigma(g)(2)2 sigma(u)(2)1 pi(u)(4)1 pi(g)(4)) of MX2- was observed. Analysis of the polestrength showed that all electron detachment channels in this study can be described as primarily one-electron processes.