[3] Lykketoft matriculated in mathematics from Frederiksberg Gymnasium, an upper secondary school, in 1964 and went on to study at the University of Copenhagen.

At Copenhagen University Lykketoft became a member of Frit Forum, the Social Democratic student organisation.

From 1975 to 1981 he was department head in "The Economic Council of the Labour Movement", a Danish think tank made up of trade union leaders and Social Democratic MPs.

Five years later he was more successful when his new candidate, Poul Nyrup Rasmussen, challenged and defeated Auken at an extraordinary congress of the Social Democrats.

[6] After the resignation of the Conservative/Liberal government in January 1993 Lykketoft became Finance Minister in the cabinets of Poul Nyrup Rasmussen (I, II, III, IV).

After the 2019 Danish general election, Lykketoft stepped down from his position as an MP in the Folketing, bringing an end to his nearly 40-year tenure.

[8] As President or Speaker of the Folketing he has been on official visits to Turkey (2014), Iceland (2014), Slovakia (2013),[9] Greece (2013), The Bundestag in Berlin (2013) and The United States Congress in Washington (2012).

He has also been on work visits to Mexico (2014), Palestine (2014),[10] Mongolia (2013), Burma, (2013), Albania (2012), Bulgaria (2012), Vietnam (2012) and Indonesia (2012).

[11] In March 2013, Lykketoft was nominated for the position of President of the United Nations General Assembly by the Danish government.

On 15 June 2015, he made history by becoming the first Dane ever to be elected to this prestigious position, and oversaw the Seventieth session of the United Nations General Assembly.

[12] During his presidency, he would not resign as a Danish MP but rather take a leave of absence returning to the Folketing after his UN appointment has ended.