RPC detectors play a crucial role in triggering events with muons in the ATLAS central region; it is facing a significant upgrade in view of the HL-LHC program. In the next few years, 306 triplets of new generation RPCs with a 1 mm gas gap (instead of 2 mm) will be installed in the innermost region of the ATLAS Muon Barrel Spectrometer, increasing the number of tracking layers from 6 to 9, doubling the trigger lever arm and increasing the coverage. Innovative front-end electronics will allow to operate the RPCs with an order of magnitude less of average charge. Both sides of RPCs are read out by strip panels and the second coordinate is reconstructed from the time difference of signal drift at opposite detector ends. The expected time resolution is approximately 300 ps; the possibility of a stand-alone Time of Flight measurement will have a huge impact on ATLAS searches for long-lived particles. An overview and the present status of the ATLAS RPC Phase II project is presented.