Shubnikov–de Haas, quantum Hall effect, and cyclotron resonance measurements revealed the existence of a high mobility, two‐dimensional electron gas at the Ga0.47In0.53As/InP heterointerface grown by chemical beam epitaxy. Enhanced electron mobilities were as high as ∼130×103cm2/V s at 4.2 K. A striking feature in the data which also indicates that the sample is of high quality is the large number of Shubnikov–de Haas oscillation periods observed. Oscillations were observable up to a Landau filling factor of around 50, corresponding to a Landau level index of 25.