Electronic Journal of Differential Equations, Vol. 2025 (2025), No. 10, pp. 1-60. Title: A priori estimates for the linearized relativistic Euler equations with a physical vacuum boundary and an ideal gas equation of state Author: Brian B. Luczak (Univ. of Chicago Laboratory Schools, Chicago, IL, USA) Abstract: In this article, we will provide a result on the relativistic Euler equations for an ideal gas equation of state and a physical vacuum boundary. More specifically, we will prove a priori estimates for the linearized system in weighted Sobolev spaces. Our focus will be on choosing the correct thermodynamic variables, developing a weighted book-keeping scheme, and then proving energy estimates for the linearized system. Submitted November 27, 2024. Published January 27, 2025. Math Subject Classifications: 35Q75, 35Q35, 35Q31, 35R37. Key Words: Relativistic Euler equations; physical vacuum boundary; ideal gas equation of state.