This article does not concern whip (implement) or walks plus hits per inning pitched.
In politics, a Whip is a member of a political party in a legislature whose task is to ensure that members of the party attend and vote as the party leadership desires. The term originated in the Parliament of the United Kingdom and derives from the "whipper-in" at a fox hunt. Whip is also used to mean the voting instructions issued to members by the Whip.

The Government Chief Whip in the House of Commons is assited by the Deputy Chief Whip, Whips, and Assistant Whips. To provide seats at the Cabinet, the senior Whips are given offices in the Government. The Chief Whip is usually appointed as Parliamentary Secretary to the Treasury, the Deputy Chief Whip as Treasurer of HM (Her Majesty's) Household, two Whips as Comptroller of HM Household and as Vice-Chamberlain of HM Household, and the remaining Whips as Lords Commissioners of the Treasury. (Assistant Whips, and, of course, Whips of other parties, generally do not receive such appointments.)

A similar arrangement exists for Whips in the House of Lords. The Government Chief Whip is usually appointed Captain of the Honourable Corps of Gentlemen-at-Arms, while the Deputy Chief Whip is usually appointed Captain of the Queen's Bodyguard of the Yeomen of the Guard. Other Whips, who are fewer in number due to the decreased importance of party discipline in the Lords, are appointed Lords in Waiting if men and Baronesses in Waiting if women.

In the UK Parliament the importance of a vote is indicated by underlining of items on the whip paper. A "one-line whip" indicates that MPs may vote as they please. "Two-line whips" indicate an expectation that MPs vote as the party directs. Pairing (the practice whereby a member of one party chooses to not vote because of the opposite party is absent, essentially nullifying the effect of the absence) is allowed. "Three-line whips" are reserved for the most important matters; MPs must attend and vote with their party, and no form of pairing is allowed. Disregarding a "three-line whip," even by failing to attend the session, is a serious matter and may result in "withdrawal of the whip", which is a form of expulsion from the party.

The U.S. House of Representatives has a Majority Whip as well as a Minority Whip.