Abstract: The concept of higher-dimensional gravity has been a cornerstone of string theory, braneworld models, and modified gravity theories, suggesting that our four-dimensional spacetime may be embedded in a higher-dimensional structure. While these theories have traditionally been confined to the realm of mathematical physics, recent advances in gravitational wave astronomy, black hole imaging, and precision cosmology offer potential observational avenues for testing the existence of extra dimensions. This paper explores the role of string-theoretic compactifications, Kaluza-Klein modes, and braneworld scenarios in shaping gravitational interactions, dark matter models, and early-universe physics. We examine possible observational signatures of higher-dimensional gravity, including deviations in gravitational wave dispersion, modifications to Newton’s inverse-square law, and exotic black hole geometries. Additionally, we assess the constraints imposed by particle physics experiments, cosmological surveys, and astrophysical probes on theories that extend gravity beyond four dimensions. Key Highlights: Theoretical foundations of higher-dimensional gravity in string theory and braneworld models. Predictions of extra-dimensional effects on gravitational waves, black holes, and cosmology. Experimental constraints from gravitational lensing, dark matter phenomenology, and precision tests of gravity. Potential modifications to the cosmological constant problem and dark energy models. Prospects for future observational validation with high-energy physics and next-generation gravitational wave detectors. By combining high-energy theoretical physics with astrophysical observations, this paper investigates whether higher-dimensional gravity can be tested using current and future experimental data, providing a bridge between string theory and real-world physics. Keywords: Higher-dimensional gravity, string theory, extra dimensions, braneworld cosmology, Kaluza-Klein theory, gravitational waves, modified gravity, dark matter, cosmology, black hole physics.