This paper describes a new phase unwrapping algorithm based on morphological image processing. A region of interest corresponding to the areas where interferences occur is first extracted. This is achieved by processing the input interferograms with a combination of morphological closing and opening operators. The boundaries of the wrapped fringes are then enhanced by two gradient operators: morphological gradient by erosion for the fringe boundaries with high values and morphological gradient by dilation for the fringe boundaries with low values. Gaps along the boundaries which would lead to errors in the unwrapped phase map are filled in by the watershed transformation. Finally, the wrapped phase map is unwrapped by means of a region growing procedure based on priority queue data structures.