In broad terms, political corruption is when government officials use their governmental powers for illegitimate private gain. Misuse of government power for other purposes, like repression of political opponents and general police brutality, is not considered political corruption. Illegal acts by private persons or corporations not directly involved with the government is not considered political corruption either. Illegal acts by officeholders constitute political corruption only if the acts are directly related to their official duties.

All forms of government are susceptible to political corruption. Forms of corruption vary, but include bribery, extortion, cronyism, nepotism, patronage, graft, and embezzlement. While corruption may facilitate criminal enterprise such as drug trafficking, money laundering, and trafficking, it is not restricted to these organized crime activities. In some nations corruption is so common that it is expected when ordinary businesses or citizens interact with government officials. The end-point of political corruption is a kleptocracy, literally "rule by thieves".

What constitutes illegal corruption differs depending on the country or jurisdiction. Certain political funding practices that are legal in one place may be illegal in another. In some countries, government officials have broad or not well defined powers, and the line between what is legal and illegal can be difficult to draw.

Bribery around the world is estimated at about $1 trillion (£494bn) and the burden of corruption falls disproportionately on the bottom billion people living in extreme poverty.