Mr. O’Sullivan is a journalist, author, lecturer and broadcaster. He is President of the Danube Institute in Budapest, Assistant Editor of the Hungarian Review, English Edition as well as International Editor of Quadrant Magazine , Sydney, Australia, co-founder of Twenty-first Century Initiatives, a Washington, D. C. based think tank, and a Fellow of the National Review Institute.

His book, ""The President, the Pope, and the Prime Minister"" on the roles played by Pope John Paul II, President Reagan and Prime Minister Thatcher in the collapse of communism has been published in seven languages.

In 1987-88 he served as a Special Adviser to Prime Minister Margaret Thatcher in Downing Street.  During this period and after he left Downing Street, he served informally as a regular speech-writer for the Prime Minister. He was the principal author of the 1987 Conservative election manifesto. Later he was one of the small team that assisted Lady Thatcher in the writing of her two volumes of memoirs. And for several years in the 1990s he served both as an informal advisor to Lady Thatcher and as a member of the Academic Advisory Board of the Thatcher Foundations.

John O'Sullivan is the former Executive Editor of Radio Free Europe and Radio Liberty in Prague and a Vice-President of the RFERL Corporation.

He served as editor-in-chief of National Review in New York City magazine for almost a decade until 1998.

He is the founder and co-chairman of the New Atlantic Initiative, an international bipartisan effort dedicated to reinvigorating and expanding the Atlantic community of democracies. Launched at the Congress of Prague in May 1996 by President Vaclav Havel and Lady Thatcher, it played a major role in bringing the countries of Central and Eastern Europe into NATO.

He is a frequent contributor to papers on both sides of the Atlantic and frequently lectures on British and American politics.