O'Neill v Phillips is a United Kingdom law case, under s.459 Companies Act 1985, on an action for unfair prejudice. Mr Phillips was the owner of a company called as Pectel Ltd. The company specialised in stripping set of naturally occurring silicate minerals called as asbestos from buildings. In 1983, Mr O'Neill joined the company and started working for it.

Mr Phillips was very impressed with the work of Mr O'Neill and made him a director of the company and gave him 25% of the company's shares. In an informal chat between the two, Mr Philips said that he hoped that Mr O'Neill could one day handle the whole management and then would be getting 50% of the company's profit.

This actually happened, Mr. Phillips retired and Mr. O'Neill ran the company. But, after five years the company went into decline. Phillips returned back and took the business control.

O'Neill was miffed. In 1990, he started his own company in Germany and filed a petition against Phillips for unfair prejudicial conduct, for the termination of equal sharing of profit and rejecting the agreement for the allotment of more shares. But, the petition was rejected by the judge on both grounds. Also, it was held that the shares of O'Neill were unaffected and he suffered nothing as a member of the company. However, O’Neill won his appeal in the court of Appeal.

A leading judgement was given by Lord Hoffman, with which Lords Clyde, Jauncey, Hobhouse and Hutton concurred. The most important characteristics of the case filed by Mr O'Neill was that Mr Phillips had never really agreed to transfer the company's share to Mr O'Neill. As to capacity, even though insignificant after determining that there had been no agreement, Lord Hoffmann, disagreeing with the first instance judge, pointed out that Mr O'Neill may have had a claim in his shareholder capacity because he had invested his time and money into the company.