Zitat • Chlorogenic acid (CGA) ameliorates rheumatoid arthritis in CIA mice in a gut microbiota-dependent manner. • CGA reshapes gut microbiota composition, notably enriching Lactobacillus and promoting indolelactic acid (ILA) production. • CGA restores the Treg/Th17 balance in CIA mice, contributing to its immunomodulatory effects. • The anti-inflammatory effect of ILA is mediated through inhibition of NF-κB p65 phosphorylation. • This study reveals a novel mechanism by which CGA targets the gut microbiota–metabolite–immune axis to treat RA.