<p>International mobility is often viewed as a driver of innovation, diversity, and sustainability in Science, Technology, Engineering, and Mathematics (STEM) fields. However, less attention has been paid to how migrant students and professionals experience belonging, recognition, and identity construction within host institutions, particularly from an intersectional perspective. This study examines how migrant students and professionals in STEM construct their identities and experience belonging at a public university in Spain. Drawing on an intersectional perspective, the research is based on qualitative data from 18 semi-structured interviews with participants from diverse STEM disciplines and national backgrounds. Thematic analysis identified four main dimensions: (1) identity construction; (2) sense of belonging; (3) structural, cultural, and linguistic barriers; and (4) migrant contributions. Findings show that belonging operates as a conditional and negotiated process, shaped by institutional recognition, legal status, and intersecting factors such as gender, race, and language. Participants reported legal, bureaucratic, linguistic, and cultural challenges, particularly affecting women and racialized migrants from the Global South. At the same time, they highlight cognitive, cultural, and relational contributions that enrich STEM environments. The study contributes to debates on equity and diversity in STEM and underscores the institutional responsibility to foster a sense of belonging in higher education.</p>