To new triterpenes, trichomycins A (1) and B (2), were purified from the new species Tricholoma sp. AU1 by activity-guided fractionation following their antibacterial activity. The two compounds were found to have a hitherto unreported triterpenoid skeleton. The structures and relative stereochemistry of 1 and 2 were determined through extensive 2D NMR spectroscopy, while the inhibitory activity of 1 and 2 against two Gram-positive and two Gram-negative bacteria and a mammalian cell line was determined.