The SKYMAP Star Catalog System consists of a Master Catalog stellar database and a collection of utility software designed to create and maintain the database and to generate derivative mission star catalogs (run catalogs). It contains an extensive compilation of information on almost 300000 stars brighter than 8.0 mag. The original SKYMAP Master Catalog was generated in the early 1970's. Incremental updates and corrections were made over the following years but the first complete revision of the source data occurred with Version 4.0. This revision also produced a unique, consolidated source of astrometric information which can be used by the astronomical community. The derived quantities were removed and wideband and photometric data in the R (red) and I (infrared) systems were added. Version 3 of the SKY2000 Master Catalog was completed in May of 2000 and represents an incremental but substantial improvement over Version 2 (Cat. <V/102>). A global replacement of photovisual (ptv) and photographic (ptg) magnitudes and of Henry Draper spectral types was performed using as sources the SAO Catalog, the PPM catalogs, and the HD catalogs. Several hundred entries previously lacking them now have CCD ST magnitudes from the star tracker onboard the SWAS spacecraft (transformed to the photometric system defined by the RXTE CCD ST data in SKY2000 Version 2). Several thousand missing HD catalog identifiers (mostly for HD Extension stars) were added, and several hundred missing variable star identifiers were added. 61 stars bright enough for inclusion in SKY2000 were added, bringing the total number of entries in the SKY2000 Version 3 Master Catalog to 299,160 (299,161 in Rev. 1).