Sir Stephen Rothwell O'Brien, KBE (born 1 April 1957) is a British politician and diplomat who was the United Nations Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator.

He was first elected in a by-election in July 1999, after Alastair Goodlad was made British High Commissioner in Australia by Tony Blair and thus had to leave Parliament.

A member of the Conservative Party, within the Conservative-Liberal Democrat Coalition he was appointed as the Parliamentary Undersecretary of State in the Department for International Development.

In 2000, he introduced a Private Member's Bill for Honesty in Food Labelling (country of origin and standards of production).

[6] In January 2016, 112 doctors, humanitarian workers, and civil society members in Syria addressed an open letter to O'Brien criticizing OCHA for failing to meet urgent humanitarian needs created by the Syrian Civil War,[7] citing a report by UN Secretary General Ban Ki-moon which stated that the combined food, medical aid (insulin), and non-food items to successfully delivered to besieged areas in Syria in 2015 was enough for only 0.7% of the UN's estimated 212,000 people living under siege.

[8] O'Brien said in a note to correspondents that his office pledged to engage besieged populations and would continue to work tirelessly to bring lifesaving aid to those in need in Syria.

In an op-ed about the summit, O'Brien wrote: "To end need, we must stop thinking about relief and development as a sequence.

"[10] O'Brien was appointed Knight Commander of the Order of the British Empire (KBE) in the 2017 Birthday Honours for services to the United Nations and humanitarian affairs.