Water repellency is an attractive topic in the industrial and fundamental fields. Therefore, the evaluation of the surface properties is indispensable using contact angles and surface free energy. In 1805, Young suggested and discussed the three-phase contact line of the equilibrium droplet on a flat solid substrate and the sum of the mechanical surface tensions. Later, numerous researchers have developed interpretation of surface tensions and quantitative methods to evaluate surface tensions of solid substrates. Water repellency is classified into chemical hydrophobicity and physical water repellency. For chemically hydrophobic surfaces, polymers with perfluoroalkyl groups and other fluorine functional groups, poly(dimethyl siloxane), and poly(3-hexylthiophene) have been investigated, and surfaces with low surface free energy and large hydrophobicity have been reported. In physical water repellency, surfaces with fractal “lotus” structure have been suggested, and various structural parameters have a large impact on their water-repellency behavior. In addition, recently omniphobic surface with hydrophobicity and lipophobicity has been suggested as slippery liquid-infused porous surface and the surface possessed high contact angles and low roll-off angles.