Graphene, a two-dimensional material, exhibits a 100-fold anisotropy in thermal conductivity between in-plane and out-of-plane directions. Its high in-plane thermal conductivity is due to strong covalent sp² bonding, while out-of-plane heat flow is limited by weak van der Waals interactions. This review discusses graphene's thermal properties, including specific heat, thermal conductivity (from diffusive to ballistic limits), and the influence of substrates, defects, and atomic modifications. It highlights practical applications, such as graphene transistors and interconnects, which benefit from high in-plane thermal conductivity. However, weak thermal coupling with substrates leads to significant dissipation bottlenecks. Heat flow in graphene can be tuned through phonon scattering by substrates, edges, or interfaces. The unique thermal properties of graphene arise from its 2D nature, offering opportunities for new discoveries in heat flow physics and thermal management applications. Graphene's thermal properties are influenced by its 2D structure and lattice vibrations. The phonon dispersion of graphene includes three acoustic (A) and three optical (O) phonon modes. The in-plane acoustic modes (longitudinal and transverse) have linear dispersion, while the out-of-plane flexural modes have quadratic dispersion. These modes contribute to graphene's unique thermal properties. The specific heat of graphene is dominated by phonons and is slightly higher than that of graphite and diamond at low temperatures. The in-plane thermal conductivity of graphene is among the highest of any known material, reaching 2000-4000 W m⁻¹ K⁻¹ for freely suspended samples. However, when in contact with a substrate or confined in graphene nanoribbons, thermal conductivity decreases significantly due to phonon scattering. The thermal conductivity of graphene is highly dependent on its environment. The in-plane thermal conductivity is high, but the out-of-plane thermal conductivity is limited by weak van der Waals interactions. The thermal conductivity of graphene can be tuned by modifying its structure, such as introducing defects, edges, or isotopic impurities. The thermal conductivity of graphene can also be influenced by its size and geometry, with smaller samples exhibiting higher thermal conductivity due to reduced phonon scattering. The thermal properties of graphene have important implications for its use in nanoscale devices and interconnects. Despite its high thermal conductivity, graphene devices can experience significant self-heating under high-field and high-temperature conditions. The thermal conductivity of graphene is limited by its interfaces, contacts, and surrounding materials, which are often thermal insulators. To mitigate this, 3D architectures incorporating carbon nanotube (CNT)-pillared graphene networks, interconnected CNT truss-like structures, and networked graphene flakes can be used to enhance out-of-plane thermal conductivity. The thermal properties of graphene are highly tunable, offering potential applications in both high thermal conductivity and low thermal conductivity materials. The unique thermal properties of graphene, including its highGraphene, a two-dimensional material, exhibits a 100-fold anisotropy in thermal conductivity between in-plane and out-of-plane directions. Its high in-plane thermal conductivity is due to strong covalent sp² bonding, while out-of-plane heat flow is limited by weak van der Waals interactions. This review discusses graphene's thermal properties, including specific heat, thermal conductivity (from diffusive to ballistic limits), and the influence of substrates, defects, and atomic modifications. It highlights practical applications, such as graphene transistors and interconnects, which benefit from high in-plane thermal conductivity. However, weak thermal coupling with substrates leads to significant dissipation bottlenecks. Heat flow in graphene can be tuned through phonon scattering by substrates, edges, or interfaces. The unique thermal properties of graphene arise from its 2D nature, offering opportunities for new discoveries in heat flow physics and thermal management applications. Graphene's thermal properties are influenced by its 2D structure and lattice vibrations. The phonon dispersion of graphene includes three acoustic (A) and three optical (O) phonon modes. The in-plane acoustic modes (longitudinal and transverse) have linear dispersion, while the out-of-plane flexural modes have quadratic dispersion. These modes contribute to graphene's unique thermal properties. The specific heat of graphene is dominated by phonons and is slightly higher than that of graphite and diamond at low temperatures. The in-plane thermal conductivity of graphene is among the highest of any known material, reaching 2000-4000 W m⁻¹ K⁻¹ for freely suspended samples. However, when in contact with a substrate or confined in graphene nanoribbons, thermal conductivity decreases significantly due to phonon scattering. The thermal conductivity of graphene is highly dependent on its environment. The in-plane thermal conductivity is high, but the out-of-plane thermal conductivity is limited by weak van der Waals interactions. The thermal conductivity of graphene can be tuned by modifying its structure, such as introducing defects, edges, or isotopic impurities. The thermal conductivity of graphene can also be influenced by its size and geometry, with smaller samples exhibiting higher thermal conductivity due to reduced phonon scattering. The thermal properties of graphene have important implications for its use in nanoscale devices and interconnects. Despite its high thermal conductivity, graphene devices can experience significant self-heating under high-field and high-temperature conditions. The thermal conductivity of graphene is limited by its interfaces, contacts, and surrounding materials, which are often thermal insulators. To mitigate this, 3D architectures incorporating carbon nanotube (CNT)-pillared graphene networks, interconnected CNT truss-like structures, and networked graphene flakes can be used to enhance out-of-plane thermal conductivity. The thermal properties of graphene are highly tunable, offering potential applications in both high thermal conductivity and low thermal conductivity materials. The unique thermal properties of graphene, including its high