Jens Otto Krag (September 15, 1914 – June 22, 1978) was a Danish politician. He was Prime Minister from 1962 to 1968 and again from 1971 to 1972.

Krag was born in Randers, Denmark. He joined the Danish Social Democratic Party youth organization in 1930 and rose through the ranks of the party. In the 1930s he moved to Copenhagen and studied economics at the University of Copenhagen while remaining very active in the party.

During World War II, he was Danish supply director and advisor to the labor unions on economic matters. He was elected to Parliament (Folketinget) in 1947 and became Commerce Minister. He supported the strengthening of the Danish military and Danish membership of NATO in 1949.

In 1950 Krag resigned from Parliament partially due to a conflict with Vilhelm Buhl and H.C. Hansen and, in order to become more fluent in the English language and see more of the world, requested a position at the Danish embassy in the United States. He received the position, and was in America until 1953 when he was re-elected to parliament and became a minister without portfolio. He was minister of the new department of foreign economic affairs from 1953 until 1958 and Foreign Minister from 1958 until 1962.

In September 1962 he succeeded Viggo Kampmann as Prime Minister and leader of the Danish Social Democratic Party. He was Prime Minister until February 1968 when the Social Democrats lost power. He became Prime Minister again in 1971 when his party returned to power.

Less than a year into his first term as prime minister, the opposition held a referendum which rejected a set of land laws already passed by Krag's government.

During his second term as Prime Minister, Krag campaigned particularly for European cooperation and unity. He sponsored a referendum for Denmark to join the European Economic Community. In 1972 the referendum passed, but the nation was divided over the issue, and Krag resigned, claiming that he had become tired of politics. His last role in public life was as the European Common Market representative to the United States from 1974 until 1975.

Krag is widely recognised as one of the greatest politicians of all time in Denmark. He was in the front - line of politics for 25 years, holding high ministerial offices for most of that time. He managed to raise Denmark's profile on the world stage, striking up strong relationships with fellow European leaders as well as American presidents Kennedy and Johnson. His list of political achievements is also one of the most impressive, overseeing one of the longest periods of economic expansion in Danish history. However, his largest achievement, and the one he himself was most proud of, was taking Denmark into the European Economic Community in 1972. With that task accomplished he felt he could retire at a high point.

Krag was at one and the same time one of the most charismatic and withdrawn Danish politicians ever. He never enjoyed the attention he had to subject to, and many people found him rather arrogant. According to his most thorough (and quite sympathetic) biographer (Bo Lidegaard, Krag I-II, 2001/2002) he never truly settled into the role as a politician, always considering himself on the way 'to somewhere else'. Apparently the post he always dreamed of holding was that of governor of the central bank. Only when he had definitively quit politics in 1972 did he start realising that he would miss it. He didn't manage to fill that space during his remaining years.

His private life was very colourful, but ultimately rather sad. In addition to fathering a child outside wedlock, he was married twice. Krag has a daughter, Astrid Helene (born 1962), by his second wife Helle Virkner. Both marriages ended in divorce, largely due to his own persistent infidelity. Already during his time in politics he struggled with alcoholism, an illness that became more pronounced after his retirement. He died of heart failure in Skiveren, Denmark, at the age of 63.

In the Danish TV series Krøniken (2004 – 2006) he was portrayed by the actor Lars Mikkelsen.