Abstract
Using the renormalization-group method of Derrida, Gervois, and Pomeau, we have extended the calculation of the Feigenbaum universal bifurcation ratio to third order. The calculated values for the limit point and the bifurcation ratio are, respectively: a*=1.4011487 and δ=4.6753244, which agree extremely well with the exact values: a*=1.4011551 and δ=4.6692011.