An unusually large Alligator mississippiensis (American Alligator) was harvested in Alabama in 2014. We report on the animal's length and mass, and document the techniques used to obtain those measurements. We compare our measurements to other extreme lengths and weights reported for the species. We show that the size of the American Alligator is consistent with known allometric relationships of head length, total length, snout—vent length, tail girth, and weight. The specimen's straight-line total length of 450.0 cm (14 ft 9.25 in) makes it the longest officially measured American Alligator for Alabama and arguably the longest credible record for the species. We recommend using standardized techniques, particularly the straight-line total-length measurement, for documenting record-length or near-record-length American Alligators.