Per- and polyfluoroalkyl substances (PFAS) are a large group of man-made chemicals, defined by the Organisation for Economic Co-operation and Development (OECD) as any compound with a (-CF3) or (-CF2-) moiety. This strong carbon-fluorine bond renders these compounds resistant to degradation and imparts hydrophobic and oleophobic properties. These physico-chemical properties are highly attractive to industry, with PFAS being utilised in a range of industrial sectors including chemical manufacturing, electronics, pharmaceuticals, and firefighting foams as well as coatings on consumer goods. However, these same properties contribute to the persistence of PFAS in the environment. Widespread use and resistance to degradation have resulted in PFAS becoming ubiquitous in the natural environment. Even in areas without fluorochemical production, such as Ireland, PFAS can enter the environment through industrial and municipal wastewater, firefighting activities, and urban runoff, often travelling through stormwater networks before being discharged to surface waters. This study aimed to explore the influence of stormwater outfalls on the concentration of 33 PFAS in the Liffey Estuary, Dublin, Ireland. Sub-kilometer sampling was conducted at individual outfalls along the river to assess variability in PFAS loadings. Water samples were extracted by solid phase extraction using Oasis WAX cartridges, and analysed by high-pressure liquid chromatography (Sciex Exion) coupled with time-of-flight mass spectrometry (Sciex 5600+ triple TOF-MS). Twenty-four PFAS were detected across the estuary, including long-chain compounds and their short-chain replacements. Total PFAS concentrations ranged from 6.20 to 91.48 ng/L, with highest total concentrations downstream of waste treatment facilities. Spatial variation in PFAS class profiles was evident across the upper and lower estuary, with the number of PFAS detected ranging from 2 to 14 compounds. Detections and concentrations varied markedly between outfalls within a few hundred metres of each other. Multivariate analysis indicated that stormwater outfalls act as a diffuse source of PFAS in the Liffey Estuary, along with unique PFAS profiles being attributed to localised inputs such as waste facilities and marina activities. These findings highlight the need for high-resolution spatial monitoring to improve PFAS source attribution and understanding of mobility pathways in urban surface waters.