The remarkable 13.6 TeV center-of-mass energy achieved by the LHC in 2022 has enabled searches for increasingly heavier states produced in particle collisions. However, plenty of interesting new physics scenarios feature much lighter particles, which can nevertheless be experimentally probed with the intense accelerator beams available today. In this talk, I will describe two efforts to investigate new low-mass processes with complementary experimental approaches, focusing on searches for sub-GeV dark matter models. The first is a new fixed-target experiment called PADME that seeks to identify MeV-scale dark photon production with a positron beam in Frascati, Italy. The second is the novel “trigger-level analysis” technique of the CMS and ATLAS experiments at CERN, which can be used to probe very rare low-mass phenomena. I will discuss various analyses that are made possible by this technique, including a new CMS search for sub-GeV dark photons that could yield world-leading sensitivity in this parameter space. Finally, I will discuss how both collider and fixed-target experiments can be used to confirm or refute the “X17” hypothesis, which predicts a new protophobic vector boson with a mass of only 17 MeV to explain a series of recent anomalies observed in nuclear experiments.