The catalog of 4195 optically confirmed Sunyaev-Zel'dovich (SZ) selected galaxy clusters were detected with signal-to-noise > 4 in 13,211 deg<sup>2</sup> of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multi-frequency matched filter to 98- and 150-GHz maps constructed from ACT observations obtained from 2008-2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 < z < 1.91 (median z = 0.52). The catalog contains 222 z > 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ-signal vs. mass scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M<sub>500c</sub> > 3.8 x 10<sup>14</sup>M<sub>sol</sub>, evaluated at z=0.5, for clusters detected at signal-to-noise ratio > 5 in maps filtered at an angular scale of 2.40. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ-signal mass-scaling relation, such as the Dark Energy Survey (4566 deg<sup>2</sup>), the Hyper Suprime-Cam Subaru Strategic Program (469 deg<sup>2</sup>), and the Kilo Degree Survey (825 deg<sup>2</sup>). This HEASARC database table was ingested in February 2021. It contains the ACT DR5 SZ cluster catalog obtained from the LAMDBA website (<a href="https://lambda.gsfc.nasa.gov/product/act/actpol_dr5_szcluster_catalog_info.cfm#catalog">https://lambda.gsfc.nasa.gov/product/act/actpol_dr5_szcluster_catalog_info.cfm#catalog</a>). This is a service provided by NASA HEASARC .