Interaction　of　tea　phenolics　with　gut　microbiota　may　play　an　integral　role　in　the　health　benefits　of　these　bioactive　compounds,　yet　this　interaction　is　not　fully　understood.　Here,　the　metabolic　fate　of　epigallocatechin-3-gallate　(EGCG)　and　its　impact　on　gut　microbiota　were　integrally　investigated　via　in　vitro　fermentation.　As　revealed　by　ultrahigh　performance　liquid　chromatography　hybrid　quadrupole　Orbitrap　mass　spectrometry　(UHPLC-Q-Orbitrap-MS),　EGCG　was　promptly　degraded　into　a　series　of　metabolites,　including　4-phenylbutyric　acid,　3-(3′,4′-dihydroxyphenyl)propionic　acid,　and　3-(4′-hydroxyphenyl)propionic　acid,　through　consecutive　ester　hydrolysis,　C-ring　opening,　A-ring　fission,　dehydroxylation,　and　aliphatic　chain　shortening.　Microbiome　profiling　indicated　that,　compared　to　the　blank,　EGCG　treatment　resulted　in　stimulation　of　the　beneficial　bacteria　Bacteroides,　Christensenellaceae,　and　Bifidobacterium.　Additionally,　the　pathogenic　bacteria　Fusobacterium　varium,　Bilophila,　and　Enterobacteriaceae　were　inhibited.　Furthermore,　changes　in　concentrations　of　metabolites,　including　4-phenylbutyric　acid　and　phenylacetic　acid,　were　strongly　correlated　with　changes　in　the　abundance　of　specific　gut　microbiota.　These　reciprocal　interactions　between　EGCG　and　gut　microbiota　may　collectively　contribute　to　the　health　benefits　of　EGCG.　©　2020　American　Chemical　Society.