This paper quantifies the socio-economic status (SES) gradient in median lifespan for three birth cohort groups. For this, mortality models were estimated using unique data on the SES of Dutch Olympic athletes born between 1852 and 1947, and who were followed until their death (or December 2018). The empirical findings show that for the older birth cohorts (1852-1899) there were no significant differences in median lifespan between SES groups. For the middle cohorts (1900-1919), the low SES athletes had a significantly lower median lifespan of five years less compared to medium SES athletes and the median lifespans of high and medium SES athletes did not differ significantly. For the younger cohorts (1920-1947), large and statistically significant differences were found between the three SES groups: low SES athletes had a median lifespan of about six years lower than medium SES athletes, while high SES athletes had an almost five years higher median lifespan compared to medium SES athletes. These new findings, which can be reconciled with the existing literature, suggest a strong steepening of the population SES-lifespan gradient over time in the Netherlands.