Damghan University Press Journal of Holography Applications in Physics 2783-4778 5 3 2025 09 18 Journey Through Cosmic: Tsallis Holographic Dark Energy and the Deformed Starobinsky Model 50 63 1884 10.22128/jhap.2025.1041.1122 EN Fatemeh Baziar Department of Physics, Faculty of Basic Sciences, University of Mazandaran, P. O. Box 47416--95447, Babolsar, Iran 0009-0002-8821-7628 Journal Article 2025 06 30 This study investigates the intricate dynamics of Tsallis holographic dark energy within the framework of a modified Starobinsky gravity theory. The distinctiveness of the model lies in its formulation, which involves both the Ricci scalar $R$ and an additive positive term. The primary objective is to derive the equation of state parameter, a crucial element in understanding the behavior and properties of dark energy throughout the universe. To simplify and strengthen the analysis, we adopt an exponential form for the scale factor, which is commonly used in models featuring constant expansion rates due to its analytical tractability. A comprehensive stability evaluation is also carried out, with particular attention given to the squared sound speed — a critical factor in examining how fluctuations evolve within the dark energy sector. Graphical representations are employed to highlight stable regimes and to visually interpret the viability of this holographic model under modified gravitational dynamics. The findings are presented in a detailed manner, including rigorous derivations and explicit formulations that underline the theoretical consistency and potential cosmological relevance of the model. https://jhap.du.ac.ir/article_1884_6245c23089e005a36c36d5bb9949b489.pdf