<![CDATA[The rapid development of artificial intelligence (AI) has expanded opportunities for English as a Foreign Language (EFL) learning, particularly through ChatGPT as an accessible language-learning tool. Although previous studies have reported generally positive perceptions of ChatGPT among language learners, empirical evidence concerning its relationship with measurable language proficiency remains limited. This study examined the relationship between ChatGPT use and vocabulary mastery among eleventh-grade students at MAN 1 Kota Palu, Indonesia. Using a quantitative correlational design, the study involved 54 students selected through purposive sampling. Data were collected using a 20-item ChatGPT Usage Questionnaire measuring frequency of use and perceived usefulness, along with a 30-item Vocabulary Mastery Test assessing lexical knowledge. The data were analyzed using descriptive statistics, the Kolmogorov–Smirnov normality test, and Pearson's product-moment correlation. The findings showed that students generally reported moderate to high levels of ChatGPT use and perceived it as useful for vocabulary learning. However, the correlation analysis revealed a negligible positive and statistically nonsignificant relationship between ChatGPT use and vocabulary mastery (r = .020, p = .886). These findings suggest that frequent use and positive perceptions of ChatGPT do not necessarily correspond to higher vocabulary achievement. Other learner-related and contextual factors, which were not directly examined in this study, may contribute to differences in vocabulary mastery. Therefore, ChatGPT may be more appropriately viewed as a supplementary resource whose educational value depends on how it is used and integrated into meaningful language-learning activities.]]>
