Significance Statement Renal fibrosis is a common pathologic process of progressive CKD. We have provided strong evidence that PGI₂ is an important component in the kidney injury/repairing process by reducing fibrosis and protecting renal function from declining. In our study, administration of a PGI₂ analog or selective PTGIR agonist after the acute injury ameliorated renal fibrosis. Our findings provide new insights into the role of PGI₂ in kidney biology and suggest that targeting PGI₂/PTGIR may be a potential therapeutic strategy for CKD. Background Prostanoids have been demonstrated to be important modulators to maintain tissue homeostasis in response to physiologic or pathophysiologic stress. Prostacyclin (PGI₂) is a member of prostanoids. While limited studies have shown that PGI₂ is involved in the tissue injury/repairing process, its role in renal fibrosis and CKD progression requires further investigation. Methods Prostacyclin synthase (Ptgis)-deficient mice, prostaglandin I₂ receptor (Ptgir)-deficient mice, and an oral PGI₂ analog and selective PTGIR agonist were used to examine the role of PGI₂ in renal fibrosis in mouse models. We also analyzed the single-cell RNA-Seq data to examine the PTGIR-expressing cells in the kidneys of patients with CKD. Results Increased PTGIS expression has been observed in fibrotic kidneys in both humans and mice. Deletion of the PTGIS gene aggravated renal fibrosis and decline of renal function in murine models. A PGI₂ analog or PTGIR agonist that was administered after the acute injury ameliorated renal fibrosis. PTGIR, the PGI₂ receptor, deficiency blunted the protective effect of the PGI₂ analog. Fibroblasts and myofibroblasts were the major cell types expressing PTGIR in the kidneys of patients with CKD. Deletion of PTGIR in collagen-producing fibroblastic cells aggravated renal fibrosis. The protective effect of PGI₂ was associated with the inhibition of fibroblast activation through PTGIR-mediated signaling. Conclusions PGI₂ is an important component in the kidney injury/repairing process by preventing the overactivation of fibroblasts during the repairing process and protecting the kidney from fibrosis and decline of renal function. Our findings suggest that PGI₂/PTGIR is a potential therapeutic target for CKD.