Background: Bullying victimisation is of global importance due to its long-term negative consequences. We examined the prevalence of victimisation and its inequalities in 15-year-olds across 71 countries, using data from the Programme for International Student Assessment 2018. Methods: Students reported frequencies of relational, physical, and verbal victimisation during the last 12 months, which were both analysed separately and combined into a total score. Prevalence of high victimisation (> a few times a month) was estimated, followed by mean differences by gender, wealth and academic performance quintiles in each country. Meta-analyses were used to pool and examine country differences. Findings: Of the 421,437 students included 30·4% experienced victimisation, yet this varied by country—from 9·3% (Korea) to 64·8% (Philippines). Verbal and relational victimisation were more frequent (21·4%, 20.9%, respectively) than physical victimisation (15·2%). On average, boys (vs girls +0·23SD, 95%CI: 0·22–0·24), students from the lowest wealth (vs highest +0·09SD, 0·08–0·10) and with lowest academic performance (vs highest +0·49SD, 0·48–0·50) were at higher risk of victimisation. However, there was substantial between-country heterogeneity in these associations (I2 =85%–98%). Similar results were observed for subtypes of victimisation—except relational victimisation, where gender inequalities were smaller. Interpretation: Globally, bullying victimisation was high, although the size, predominant subtype and strength of associations with risk factors varied substantially by country. This highlights the need to tackle bullying victimization globally—the cross-country differences observed suggest benefits may arise from identifying and learning from countries with low prevelance and/or inequality. Funding Information: Japan Foundation for Paediatric Research. Declaration of Interests: All authors declare no competing interests. Ethics Approval Statement: Approval for the collection of the data was obtained from the PISA Governing Board, composed of representatives of OECD Members and PISA Associates. In each participating country or economy, school staff, students and parents were informed of the nature of the assessment and its use and consent provided.