We investigate the normal state of the “11” iron-based superconductor FeSe0.42Te0.58 by angle-resolved photoemission. Our data reveal a highly renormalized quasiparticle dispersion characteristic of a strongly correlated metal. We find sheet dependent effective carrier masses between ≈3 and 16me corresponding to a mass enhancement over band structure values of m∗/mband≈6–20. This is nearly an order of magnitude higher than the renormalization reported previously for iron-arsenide superconductors of the “1111” and “122” families but fully consistent with the bulk specific heat.