Few short Big Five instruments have been tested for invariance across samples from a large number of countries. To fill this gap, we measured the Big Five personality traits in probability samples (n > 1000 in each country) from Belgium, Brazil, China, France, Germany, India, Indonesia, Italy, Japan, Korea, Mexico, Nigeria, Philippines, Russia, Thailand, Turkey, UK, US, and Vietnam. We used a new, short Big Five questionnaire, based on the BFI and other short instruments after consultations and tests in diverse cultures. Across the US sample (n = 2811, nationally representative), as well as in Japan and other countries, our 15-item questionnaire yielded higher loadings on intended factors and lower cross-loadings than what has been reported for the BFI, and the BFI-2-XS in the US and worldwide. Exploratory Structural Equation Modeling of our tool recovered the Big Five, and its structure was very stable across countries, yet without metric comparability. We conclude that the Big-Five model covers important cross-cultural commonalities in the structure of personality, and our study reveals its invariant core across many countries. Yet metric comparability is compromised for some items. Cross-cultural comparisons of scores on our measure, and most likely other Big Five measures, seem premature.