This article presents a novel compact self-quintuplexing antenna architecture based on a substrate-integrated rectangular cavity (SIRC) for pentaband applications. The proposed self-quintuplexing antenna is constructed by employing an SIRC, one Pi-shaped slot (PSS), one T-shaped slot (TSS), and five $50\Omega $ microstrip feedlines. The PSS and TSS are engraved on the top of the SIRC to create five radiating patches, which are excited by five $50\Omega $ feedlines to achieve pentaband operation with self-quintuplexing characteristics. The resonating frequencies can be tuned independently based on the dimension of the radiator without disturbing other bands. A detailed parametric analysis is carried out to provide a suitable frequency tunable range and high isolation. In addition, an equivalent lumped circuit is developed to analyze the proposed self-quintuplexing antenna. To validate the proposed antenna architecture, an SIRC-based self-quintuplexing antenna operating at 2.29, 2.98, 3.65, 4.37, and 5.08 GHz is fabricated and demonstrated. The fabricated antenna offers competitive performance with a compact size of $0.173\lambda ^{2}$ , pentaband operation, high isolation of 29.31 dB, and a wide frequency tunability range from 2.29 GHz to 6.03 GHz. Furthermore, the fabricated self-quintuplexing antenna exhibits the measured realized gain of 3.59, 4.55, 3.91, 5.70, and 4.92dBi at 2.29, 2.98, 3.64, 4.37, and 5.08 GHz, respectively.