A five-level LLC resonant converter is proposed, which is composed of two three-level (TL) bridge arms, main/auxiliary transformers, resonant elements and a set of rectifier bridge. The DC side and AC side of the two TL bridge arms are parallel connected and serial connected, respectively. With different modulation methods, the converter has three different operation modes with low, medium and high voltage gains. Compared with the traditional TL LLC resonant converter, it has lower switching frequency and higher efficiency at low gain mode. Using the same resonant parameters, it has a higher voltage gain and is more suitable for wide output range. A prototype with 90–220 V output was built. The measured efficiency of the new topology was 1.9% higher than that of the traditional topology at low voltage gain mode, and three gain modes were validated.