The full color 12.1‐inch WXGA active‐matrix organic light emitting diode (AMOLED) display was, for the first time, demonstrated using indium‐gallium‐zinc oxide (IGZO) thin‐film transistors (TFTs) as an active‐matrix back plane. It was found that the fabricated AMOLED display did not suffer from the well‐known pixel non‐uniformity of luminance, even though the simple structure consisting of 2 transistors and 1 capacitor was adopted as a unit pixel circuit, which was attributed to the amorphous nature of IGZO semiconductor. The n‐channel a‐IGZO TFTs exhibited the field‐effect mobility of 8.2 cm²/Vs, threshold voltage of 1.1 V, on/off ratio of > 10⁸, and subthreshold gate swing of 0.58 V/decade. The AMOLED display with a‐IGZO TFT array would be promising for large size applications such as note PC and HDTV because a‐IGZO semiconductor can be deposited on large glass substrate (> Gen. 7) using conventional sputtering system.