税（又称税赋、税负、税捐、租税等）是指政府（或与政府等价的实体，如教会、部落首领）向纳税人（个人或企业法人）强制征收的货币或资源。税由法律强制力保证，抗拒纳税的人会受到法律惩罚。税收可以分为直接税和间接税，税收的形式可以是货币或劳动。少数国家完全不用纳税，像阿拉伯联合酋长国。

依税法缴纳的金额称为「税金」。依据不同课税对象、或是不同法律授权、或是不同纳税人可划分为不同的分类，称为税种或税目。政府依法对民间收取税收的行为称为课税；个人或企业向政府缴纳税金的行为称为纳税。政府要求纳税人在缴税期限后缴足应纳税金称为补税，政府退还溢收税金称为退税。

A tax (from the Latin taxo) is a financial charge or other levy imposed upon a taxpayer (an individual or legal entity) by a state or the functional equivalent of a state to fund various public expenditures. A failure to pay, or evasion of or resistance to taxation, is usually punishable by law. Taxes consist of direct or indirect taxes and may be paid in money or as its labour equivalent. Some countries impose almost no taxation at all, or a very low tax rate for a certain area of taxation.