KMT-2019-BLG-0335L is a Sun-like G-type star (about 0.32 solar masses, 5,778 K), 7,710 light-years from Earth. KMT-2019-BLG-0335L b is a 21.0-Jupiter-mass companion, at 1.640 AU from its star, discovered in 2023 via microlensing. Microlensing detections occur when a foreground star's gravity briefly magnifies a background source, revealing planets that are otherwise too faint and distant to observe directly. KMT-2019-BLG-0335L b orbits at roughly the distance of Mars from the Sun. At 21.0 Jupiter masses, the companion lies near the dividing line between giant planets and brown dwarfs.