Background: Late stillbirth, which occurs ≥28 weeks’ gestation, affects 1.3‐8.8 per 1000 births in high‐income countries. Of concern, most occur in women without established risk factors. Identification of potentially modifiable risk factors that relate to maternal behaviors remains a priority in stillbirth prevention research. This study aimed to investigate, in an international cohort, whether maternal sleep practices are related to late stillbirth. Methods: An Internet‐based case‐control study of women who had a stillbirth ≥28 weeks’ gestation within 30 days before completing the survey (n = 153) and women with an ongoing third‐trimester pregnancy or who had delivered a live born child within 30 days (n = 480). Bivariate and multivariate logistic regressions were used to determine unadjusted and adjusted odds ratios (OR and aOR, respectively) with 95% confidence intervals (95% CIs) for stillbirth. Results: Sleeping >9 hours per night in the previous month was associated with stillbirth (aOR 1.75 [95% CI 1.10‐2.79]), as was waking on the right side (2.27 [1.31‐3.92]). Nonrestless sleep in the last month was also found to be associated with stillbirth (1.73 [1.03‐2.99]), with good sleep quality in the last month approaching significance (1.64 [0.98‐2.75]). On the last night of pregnancy, not waking more than one time was associated with stillbirth (2.03 [1.24‐3.34]). No relationship was found with going to sleep position during pregnancy, although very few women reported settling in the supine position (2.4%). Conclusions: Long periods of undisturbed sleep are associated with late stillbirth. Physiological studies of how the neuroendocrine and autonomic system pathways are regulated during sleep in the context of late pregnancy are warranted.