ABSTRACT Macrophages mediate innate immune responses that recognise foreign pathogens, and bacterial lipopolysaccharide (LPS) recruits a signalling pathway through Toll-like receptor 4 (TLR4) to induce pro-inflammatory cytokines and reactive oxygen species (ROS). LPS activation also skews the metabolism of macrophages towards a glycolytic phenotype. Here, we demonstrate that the LPS-triggered glycolytic switch is significantly attenuated in macrophages deficient for glutathione transferase omega-1 (GSTO1, note that GSTO1-1 refers to the dimeric molecule with identical type 1 subunits). In response to LPS, GSTO1-1-deficient macrophages do not produce excess lactate, or dephosphorylate AMPK, a key metabolic stress regulator. In addition, GSTO1-1-deficient cells do not induce HIF1α, which plays a key role in maintaining the pro-inflammatory state of activated macrophages. The accumulation of the TCA cycle intermediates succinate and fumarate that occurs in LPS-treated macrophages was also blocked in GSTO1-1-deficient cells. These data indicate that GSTO1-1 is required for LPS-mediated signalling in macrophages and that it acts early in the LPS–TLR4 pro-inflammatory pathway.