Jonathan Bryan Guinness, 3rd Baron Moyne (born 16 March 1930), is a British peer, businessman and writer. A member of the Guinness family, he is the elder of the two sons of Bryan Guinness, 2nd Baron Moyne, and his first wife Diana Mitford (later Lady Mosley). Until his retirement, he was a non-executive director of Guinness plc and a merchant banker with Messrs Leopold Joseph.

Guinness was educated at Eton College and the University of Oxford. He worked as a journalist and then as a merchant banker. From 1970 to 1974 he was a member of Leicestershire County Council.

Guinness stood twice unsuccessfully as a parliamentary candidate for the Conservative Party, at both the 1973 Lincoln by-election (notable for the election of Dick Taverne) and the 1976 Coventry North West by-election.

He was a long-standing and early member (1968) of the Conservative Monday Club, serving on several of its committees. He was a member of the club's executive council in 1971, when he became chairman of their 'Action Fund'. In the spring 1972 edition of Monday World he contributed an article titled "The Club Today – Opportunities and Growing Pains". He was subsequently elected national chairman on 5 June following, fighting off challenges from Richard Body and Timothy Stroud.

The Guardian and The Times referred to his election as "a right-wing victory". At the club's annual general meeting in April 1973 Guinness retained the chairmanship for another year, defeating George Kennedy Young by 30 percent of the vote. In mid-1974 he was invited to address conservative students at Portsmouth Polytechnic, but was "prevented from entering by a solid wall of militant protesters hurling abuse". Guinness was a supporter of Rhodesia and, with John Stokes and the Lord Barnby addressed a Monday Club meeting on the issue in 1974 in Caxton Hall.

On 10 October 1989, at the Conservative Party Conference, he chaired a fringe meeting organised by the Young Monday Club, advertised as The End of the English? – Immigration and Repatriation. The other speakers were MPs Tim Janman and Nicholas Budgen.

As chairman of the club's Race Relations & Immigration Committee, he also wrote the same month to all Club members; "There has been a lot of ill-thought out agitation following events in China, urging the government to amend the British Nationality Act so as to give the right of UK residence to more than three million people from Hong Kong who hold British passports. At the time of writing the government has stayed firm on this, but it is under pressure. If you have not already done so, please write to your M.P., your local and national newspapers, or the Prime Minister expressing support for the government's stand. Remember, a passport is not a residence permit, but a travel document; and think of the sheer physical burden of housing and accommodating a sudden influx of this size."

He was also Club Vice-Chairman until late 1990 when he was replaced by Andrew Hunter, MP.