The fourth Mathematical Congress of the Americas, MCA 2025, will take place in Miami, Florida, USA; the dates are July 21-25, 2025. A list of invited speakers and other information can be found at the Congress website. Proposals to organize a special session are welcomed; the deadline is March 31, 2024. Organizational teams should have representation from two or more countries in the Americas, and proposals should be topically broad, with the potential to bring together diverse groups of researchers from multiple countries in the Americas. Proposals will be reviewed on a rolling basis, so early submission is encouraged. We have space for roughly 60 special sessions. More information and instructions for submitting a proposal may be found here.