  LUX-ZEPLIN (LZ) is a tonne-scale experiment searching for direct dark matter
interactions and other rare events. It is located at the Sanford Underground
Research Facility (SURF) in Lead, South Dakota, USA. The core of the LZ
detector is a dual-phase xenon time projection chamber (TPC), designed with the
primary goal of detecting Weakly Interacting Massive Particles (WIMPs) via
their induced low energy nuclear recoils. Surrounding the TPC, two veto
detectors immersed in an ultra-pure water tank enable reducing background
events to enhance the discovery potential. Intricate calibration systems are
purposely designed to precisely understand the responses of these three
detector volumes to various types of particle interactions and to demonstrate
LZ's ability to discriminate between signals and backgrounds. In this paper, we
present a comprehensive discussion of the key features, requirements, and
performance of the LZ calibration systems, which play a crucial role in
enabling LZ's WIMP-search and its broad science program. The thorough
description of these calibration systems, with an emphasis on their novel
aspects, is valuable for future calibration efforts in direct dark matter and
other rare-event search experiments.
