||Pressure ulcer (PU) is a chronic non-healing wound caused by continuous pressure of the bodyweight to the skin, which is often seen in spinal cord injury patients and in the bedridden elderly population. In spite of high mortality, the pathophysiology of PU remains poorly understood. We performed single-cell transcriptomic analysis of epidermal cells from PU wound-edges, and compared them with epidermal cells from the intact skin and normal acute wounds (AW) of healthy donors. We identified four keratinocyte clusters, one melanocyte cluster, and one immune cell cluster, and the cellular heterogeneity and gene expression were altered in PU. Our findings provided a high-resolution map of human PU and AW, which are likely to yield new areas for exploration of the pathophysiology of chronic wounds and development of wound therapy.