The crystal structures of three β-halolactic acids have been determined: β-chloro­lactic acid (I) (Z′ = 2), β-bromo­lactic acid (II) (Z′ = 2), and β-iodo­lactic acid (III) (Z′ = 1). The difference between the mol­ecules in the asymmetric units of I and II is due to the direction of the hydrogen bond of the alcohol group to a neighboring mol­ecule, which results in changes in the hydrogen-bond network.