Washing powder or washing powder is a kind of detergent (detergent) added for cleaning clothes, usually a chemical mixture including alkylbenzene sulfonate, similar to soap, but less affected by hard water. Although detergents are still sold as powders, liquid detergents have occupied a major market share in many countries since they were introduced in the 1950s.

Since 2012, P & G has introduced the sales of detergent pods in the United States in the form of tidal pods. Early examples of washing powder boxes included salvo tablets sold in the 1960s and 1970s.

Generally, laundry detergents contain water softeners, surfactants, bleaches, enzymes, brighteners, fragrances, and many other reagents. The formula is strongly influenced by the temperature of the clean water and varies by country.

The main components of washing powder are anionic surfactant, alkaline detergent aid, water softener and anti redeposition agent. High end detergents contain enzymes and fluorescent brighteners. Some liquid detergents contain non-ionic surfactants.

A variety of molecules and ions can be used as efficient surfactants. They are usually classified according to the charge of molecules or ions. The three categories are anionic, neutral and cationic detergents. Anionic detergents are the most common detergents in household laundry. Detergents are ions or molecules that contain both polar and nonpolar components. Polar components dissolve detergents in water, while non polar components dissolve greasy ("hydrophobic") materials, which are common targets of cleaning processes. It is estimated that 6 billion kg of detergent will be produced annually for the domestic market.