<p>Fatigue failures in additively manufactured 316L austenitic stainless steel produced using laser powder bed fusion processes are often attributed to the presence of process-related defects or surface roughness. To better investigate the role of surface roughness on fatigue properties, internal pores were mitigated using hot isostatic pressing, and strain-controlled fatigue testing was performed with the surface in the as-deposited condition. In the absence of internal defects, crack initiation was expected to occur at the surface, which displayed arithmetic mean surface roughness (<i>Sa</i>) values between 10 and 40&#xa0;µm as the build angle decreased from a vertical (90°) to a 45° orientation. Even though a decrease in average fatigue life with this increase in surface roughness was observed, there was no evidence of fatal cracks initiating from as-deposited surface asperities. Instead, widespread brittle intergranular fracture occurred within fine-grained sub-surface regions in the contour passes along the specimen perimeter that were populated by sub-micrometer-sized Cr₂N particles and nanometer-sized α-tridymite oxides that decorated the austenite grain boundaries. The width of these brittle fracture regions increased by 100&#xa0;µm as the build angle changed from 90° to 45°. At the same time, the fraction of decorated grain boundaries (30–45%) and precipitate length (up to 10&#xa0;µm) within these wider contour regions increased, driving the observed decreases in the fatigue life.</p> Graphical abstract <p></p>