The planetary boundary layer height (PBLH), of great importance in meteorology and atmospheric physics, is strongly correlated with the geographical location, the solar irradiance, the seasonal variations, and the variability of the weather phenomena. So far, several lidar techniques have been developed to detect the PBLH, besides the radio soundings, sodars, or other techniques. In this work we propose new algorithms to provide the PBLH in near real time using a three-dimensional lidar in vertical or slant pointing. We show that the proposed variable space–time and vertical decision algorithms are able to estimate the PBLH under various meteorological conditions of more than 80% of the cases studied. Furthermore, these algorithms are user friendly (user adjustable), and they work automatically at any location and period of the year for any vertically/slant pointing lidar system. These algorithms are extremely helpful for meteorologists, airport tower controllers, and atmospheric scientists and in general for the remote sensing community.