The Strategic Defense Fellows Program Act of 2023 modifies an existing fellowship program that trains future defense leaders by changing how fellows are placed into Defense Department jobs. Instead of being "assigned" to positions, fellows will now be formally "appointed" to temporary excepted service positions at the GS-10 to GS-12 pay level for one year, with an option to extend for another year. The program caps participation at 60 individuals annually with geographic diversity requirements ensuring no single region provides more than 20 percent of fellows. The legislation also adds new benefits including potential education loan repayment for eligible fellows and requires the Department of Defense to provide career development support and mentorship to help fellows advance toward senior leadership positions. Defense component leaders must annually submit placement opportunities tailored to develop fellows' leadership skills and create pathways for them to transition into permanent career positions within the department.