With the commencement of shared-risk science observations in May 2012, the Keck I laser guide star (LGS) adaptive optics (AO) system is the second LGS AO system to be commissioned at the W. M. Keck Observatory. This paper reports on the Keck I LGS AO system itself and some of the initial performance results. The Keck I system differs from the Keck II system primarily with regards to the laser and a beam transport system which projects the laser from behind the telescope's secondary mirror. The existing OSIRIS science instrument has been integrated with the Keck I system.