In times of rapid technological innovation and global challenges, the development of science, technology, engineering and mathematics (STEM) competencies becomes important. They improve the personal scientific literacy of citizens, enhance international economic competitiveness and are an essential foundation for responsible citizenship, including the ethical custodianship of our planet. The latest programme for international student assessment results, however, indicate that even in economically mature countries such as those in Europe, and the USA and Australia, approximately 20% of students lack sufficient skills in mathematics or science. This trend serves to highlight the urgent need for action in relation to STEM education. While it is widely acknowledged that mathematics underpins all other STEM disciplines, there is clear evidence it plays an understated role in integrated STEM education. In this article, we address an element of this concern by examining the role of mathematics within STEM education and how it might be advanced through three interdisciplinary approaches: (1) twenty-first century skills; (2) mathematical modelling; and (3) education for responsible citizenship. At the end of the paper we discuss the potential for research in relation to these three aspects and point to what work needs to be done in the future.