arXiv:2510.26094v1 Announce Type: new Abstract: We present Lean4PHYS, a comprehensive reasoning framework for college-level physics problems in Lean4. Lean4PHYS includes LeanPhysBench, a college-level benchmark for formal physics reasoning in Lean4, which contains 200 hand-crafted and peer-reviewed statements derived from university textbooks and physics competition problems. To establish a solid foundation for formal reasoning in physics, we also introduce PhysLib, a community-driven repository containing fundamental unit systems and theorems essential for formal physics reasoning. Based on the benchmark and Lean4 repository we composed in Lean4PHYS, we report baseline results using major expert Math Lean4 provers and state-of-the-art closed-source models, with the best performance of DeepSeek-Prover-V2-7B achieving only 16% and Claude-Sonnet-4 achieving 35%. We also conduct a detailed analysis showing that our PhysLib can achieve an average improvement of 11.75% in model performance. This demonstrates the challenging nature of our LeanPhysBench and the effectiveness of PhysLib. To the best of our knowledge, this is the first study to provide a physics benchmark in Lean4.