John Fredrik Reinfeldt (pronounced [ˈfreːdrɪk ˈrajnˌfɛlt] ( listen); born 4 August 1965) is the Prime Minister of Sweden, leader of the liberal conservative Moderate Party and former President of the European Council.

A native of Stockholm County, Reinfeldt joined the Moderate Youth League in 1983, and by 1992 had risen to the rank of chairman, a position he held until 1995. He has been a Member of Parliament since 1991, representing his home constituency. Following the 1994 defeat of the Moderate-led coalition government, Reinfeldt adopted a critical stance against the party leadership under Carl Bildt, which resulted in isolation within the party. However, following a change of leadership in 1999 and a bad result in the 2002 election, Reinfeldt gradually gained influence within the Moderate Party.

Reinfeldt was elected party leader on 25 October 2003, succeeding Bo Lundgren. Under his leadership, the Moderate Party has transformed its policies and oriented towards the centre, branding itself "the New Moderates" (Swedish: Nya moderaterna). Following the general elections held on 17 September 2006, Reinfeldt was elected Prime Minister by the new parliament on 5 October and presented his cabinet the following day. Together with the three other political parties in the centre-right Alliance for Sweden, Reinfeldt presides over a coalition government with the support of a narrow majority in the parliament. At the age of 41, he was the third youngest person to become Prime Minister of Sweden. After the 2010 election Reinfeldt's government was reduced to a minority government but also becoming the first centre-right government since before World War II to be re-elected, making Reinfeldt the first Moderate politician elected to two consecutive terms as Prime Minister. He is also the longest-serving Moderate Prime Minister in Swedish history.