Nostalgia is a social, self-relevant, and bittersweet (although mostly positive) emotion that arises when reflecting on fond past memories and serves key psychological functions. The majority of evidence concerning the prevalence, triggers, and functions of nostalgia has been amassed in samples from a handful of largely Western cultures. If nostalgia is a fundamental psychological resource, it should perform similar functions across cultures, although its operational dynamics may be shaped by culture. This study (N = 2606) examined dispositional nostalgia, self-reported triggers of nostalgia, and functions of experimentally-induced nostalgia in young adults across 28 countries and a special administrative region of China (i.e., Hong Kong). Results indicated that nostalgia is frequently experienced across cultures, albeit better valued in more-developed countries (i.e., higher national wealth and life-expectancy). Nostalgia is triggered by psychological threats (especially in warmer countries), sensory stimuli (especially in more-developed countries), and social gatherings (especially in less-developed countries). The positive or negative affect prompted by experimentally-induced nostalgia varied by country, but was mild overall. More importantly, recalling a nostalgic (vs. ordinary) memory increased social connectedness, self-continuity, and meaning in life across cultures. In less-developed countries, recalling an ordinary memory also conferred some of these functions, reducing the effect size of nostalgia. Finally, recalling a nostalgic (vs. ordinary) memory augmented state satisfaction with life in countries with lower quality of living (i.e., lower life-expectancy and life-satisfaction). Overall, findings confirm the relevance of nostalgia across a wide range of cultures and indicate cultural nuances in its functioning.