威廉·佩蒂·菲茨莫里斯，第一代兰斯当侯爵 William Petty Fitzmaurice，1st Marquess of Lansdowne（1737年5月2日~1805年5月7日），以第二代谢尔本伯爵的称号更为人所知。英国首相，辉格党领袖。

威廉·佩蒂出身于爱尔兰的一个古老家族，该家族长期是克里地区的领主。他的爷爷托马斯·菲茨莫里斯1723年承袭克里伯爵爵位，娶威廉·佩蒂爵士的女儿为妻子。因威廉·佩蒂爵士死后没有子嗣，遗产继承给他的外甥第一代谢尔本伯爵约翰·菲茨莫里斯，后者于1751年在名字中加入“佩蒂”。兰斯当侯爵威廉·佩蒂即为此人之子。

William Petty, 1st Marquess of Lansdowne KGPC (2 May 1737 – 7 May 1805), known as The Earl of Shelburne between 1761 and 1784, by which title he is generally known to history, was an Irish-born British Whig statesman who was the first Home Secretary in 1782 and then Prime Minister 1782–1783 during the final months of the American War of Independence. He succeeded in securing peace with America and this feat remains his most notable legacy. He was also well known as a collector of antiquities and works of art.