This study develops a novel model of endogenous sovereign debt maturity that rationalizes various stylized facts about debt maturity and the yield spread curve: first, sovereign debt duration and maturity generally exceed one year, and co-move positively with the business cycle. Second, sovereign yield spread curves are usually non-linear and upward-sloped, and may become non-monotonic and inverted during a period of high credit market stress, such as a default episode. Finally, output volatility, impatience, risk aversion, and especially sudden stops, are key determinants of maturity, both in our model and in the data.