An IBM Mainframe Developer is responsible for designing, developing, maintaining, and troubleshooting applications that run on IBM mainframe systems. They typically work with programming languages like COBOL, JCL, and SQL, and use tools such as CICS and DB2 to manage transactions and databases. Their role is critical in industries like banking, insurance, and government, where mainframes handle large-scale, high-volume processing. IBM Mainframe Developers ensure system reliability, performance, and security while also modernizing legacy systems to meet evolving business needs.