Gallium oxide (Ga2O3) materials can be fabricated via various methods or processes. It is often mentioned that it possesses different polymorphs (α-, β-, γ-, δ- and ε-Ga2O3) and excellent physical and chemical properties. The basic properties, crystalline structure, band gap, density of states, and other properties of Ga2O3 will be discussed in this article. This article extensively discusses synthesis of pure Ga2O3, co-doped Ga2O3 and Ga2O3-metal oxide composite and Ga2O3/metal oxide heterostructure nanomaterials via solution-based methods mainly sol-gel, hydrothermal, chemical bath methods, solvothermal, forced hydrolysis, reflux condensation, and electrochemical deposition methods. The influence of the type of precursor solution and the synthesis conditions on the morphology, size, and properties of final products is thoroughly described. Furthermore, the applications of Ga2O3 will be introduced and discussed from these solution processes, such as deep ultraviolet photodetector, gas sensors, pH sensors, photocatalytic and photodegradation, and other applications. In addition, research progress and future outlook are identified.