<p>Phytoremediation&mdash;the use of green plants to clean soil and water contaminated by heavy metals, metalloids and organic pollutants&mdash;is prized for being low-cost, solar-driven and ecologically benign. Its practical uptake, however, has long been constrained by two stubborn limitations: the slow pace of clean-up, dictated by the modest biomass of many metal-tolerant and hyperaccumulating plants, and the frequently low bioavailability of contaminants in the soil. A growing body of research shows that the microorganisms living in intimate association with plant roots&mdash;plant growth-promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF) and endophytes&mdash;can relieve both constraints simultaneously. This review synthesises recent progress in microbe-assisted phytoremediation. It sets out the ecological rationale for exploiting the rhizosphere, describes the two functional &ldquo;arms&rdquo; through which microbes act&mdash;direct promotion of plant growth and modulation of metal bioavailability&mdash;and surveys the specific mechanisms involved, including siderophore and organic-acid production, phosphate solubilisation, phytohormone and ACC-deaminase activity, biosorption, precipitation and biomineralisation. Representative quantitative results from inoculation trials are tabulated, and the emerging tools of omics, synthetic microbial consortia and engineered endophytes are appraised. Finally, the review confronts the principal challenge that continues to separate laboratory promise from field delivery&mdash;the unreliable establishment and persistence of introduced inocula in complex, competitive soils&mdash;and outlines the research priorities needed to close that gap.</p>