The rate coefficient of the ternary association reaction H++2H2→H3++H2$ {\mathrm{H}}^{+}+2{\mathrm{H}}_2\to {\mathrm{H}}_3^{+}+{\mathrm{H}}_2$ has been measured at a temperature of 11 K using a 22-pole ion trap. The measurements were made over the density range of 0.5–10 × 1013 cm−3 using normal hydrogen (with 1/4 p-H2 and 3/4 o-H2). We measured an apparent binary reaction rate coefficient and from the obtained linear dependence on the hydrogen density we calculated the ternary reaction rate coefficient k3 = (3 ± 1) × 10−29 cm6 s−1. From the measured data we can deduce that there exists very slow radiative association with the rate coefficient of the order of kr ≲ 3 × 10−16 cm3 s−1 at 11 K.