The goal of pan-sharpening is to increase the spatial resolution of multispectral or hyperspectral images using a high-spatial-resolution panchromatic image. The intensity-hue-saturation (IHS) method is one of the most popular pan-sharpening methods. The pan-sharpening framework of the IHS method is simple, efficient, and of high spatial quality. In this letter, we propose a nonlinear IHS method. The main concern of this letter is how to accurately estimate the intensity component. The proposed method approximates the intensity component via local and global synthesis approaches. The WorldView-2 and DEIMOS-2 data are used to evaluate the performance of the proposed method. The experimental results demonstrate that the proposed nonlinear IHS method generates high-quality pan-sharpened multispectral bands in terms of quantitatively and perceptually.