Greenmail (modeled on blackmail with reference to the color of U.S. currency) is the above-market price paid by a takeover target company to buy back shares that have been acquired, and in return the acquirer agrees to stop the takeover attempt. To combat this, some companies give thier directors' and officers' an exclusion in their policies for claims arising from the purchase of a corporation's own stock at above-market prices to resist a takeover attempt. (see poison pill)

Greenmail is also the news-letter of The Greens (NSW), a group whose fundamental objectives are to promote social, economic and political change in accordance with the four principles of:

- Ecological sustainability
- Social equality and economic justice
- Grassroots democracy
- Peace, disarmament and non violence