TOI-3877 is a Sun-like G-type star (about 1.16 solar masses, 5,731 K, 1.45 solar radii), 494 light-years from Earth. TOI-3877 b is a 0.31-Jupiter-mass companion, with an orbital period of 4.1 days, at 0.053 AU from its star, and an equilibrium temperature near 1,445 K, on an eccentric orbit (e ≈ 0.22), discovered in 2025 via transit. The inner world is a hot Jupiter — a gas giant hugging its star at a fraction of Mercury's distance — a class that forced astronomers to rethink how giant planets form and migrate inward.