Mr Gwenlan, who was born in Brecon, Powys, was previously the head of comedy at BBC TV and BBC Wales and was awarded an OBE in 2013.
He was responsible for commissioning a string of hit series, including Yes Prime Minister, Blackadder, 'Allo 'Allo and One Foot In The Grave.
He was producer on The Fall and Rise of Reginald Perrin and To The Manor Born.
Mr Gwenlan also produced and directed High Hopes for BBC Wales.
As head of comedy for BBC TV from 1983 until 1990, he was responsible for commissioning a number of classic comedy series, including Yes Prime Minister, Bread, Blackadder, 'Allo 'Allo, One Foot in the Grave, Birds of a Feather and Keeping Up Appearances.
During his tenure, the department won the Best Comedy at the Bafta awards every year and counted three Emmys among its other awards.
He admitted he could make mistakes - including trying to persuade the producer of One Foot in the Grave that Richard Wilson was not the right choice for the role of Victor Meldrew.
As a producer/director, he collected 12 Bafta nominations and two Academy awards.
He was awarded a Royal Television Society Fellowship in 1997, as well as winning six other industry awards that year, and in 1998 he was elected a fellow of the Royal Welsh College of Music and Drama.
When he produced the Christmas trilogy in 1996, more than 20 million viewers tuned in to watch Del Boy and Rodney finally become millionaires.
SOME OF THE COMEDIES WHICH GARETH GWENLAN PRODUCED OR COMMISSIONED:
Mr Gwenlan was born on a farm in Brecon but was brought up by his widowed mother and grandparents in Cefn Coed, near Merthyr Tydfil.
He trained as an actor and teacher at drama school after national service and initially started out as a theatre director in York and Derby.
He joined the BBC drama department in 1965 before moving to comedy two years later.
There he was responsible for The Fall and Rise of Reginald Perrin, To The Manor Born and Butterflies in the mid 1970s, all hits in the golden age for situation comedy.
He attributed working with Leonard Rossiter on Reginald Perrin as his first big break.
"It was a success, and the rest of my career sort of fell in behind it," he recalled.
Mr Gwenlan, receiving a lifetime achievement award from Bafta Cymru after 50 years in the business, said he had never had to work very hard.
"I've been paid all my life to indulge in my hobby," he said.
TRIBUTES TO GARETH GWENLAN:
Director of BBC Cymru Wales, Rhodri Talfan Davies, called him "quite simply one of Britain's finest comedy producers. He was a pioneer, a perfectionist".
"What finer legacy than to know you brought happiness to millions," he said.
Nicholas Lyndhurst, who played Rodney in Only Fools and Horses and also worked with Gwenlan on Butterflies and Rock and Chips, said he  was "shocked and saddened".
"He and I started working together in the late '70s, and I never found him to be anything other than a consummate professional and dedicated programme maker," he said.
"Every day working with him was a joy, culminating for me with the honour of presenting him with a Bafta fellowship a few years ago.
"He will be sadly missed by the industry he loved, and my thoughts are with his family."
John Challis who played Boycie in Only Fools, and in the spin-off The Green Green Grass, told BBC Wales Gwenlan had a "sharp eye" and an "instinct" for comedy.
"One of the great things about him, he was not only a great mover and shaker and organiser but a great mediator, getting people to work together towards one end," he said.
"He was very inventive too and was responsible for quite a few of the great moments on Only Fools and Horses. He was a great character, a bon viveur. He knew more about sitcoms than just about anybody."
Sue Holderness, who played Marlene Boyce, tweeted: "So sad to hear about Gareth Gwenlan - such a big part of my professional life. RIP."
High Hopes actor Robert Blythe paid tribute, saying: "The team of Boyd Clack writing and Gareth directing High Hopes produced some very special work.
"Gareth was hugely successful, and rightly so, in the field of situation comedy. He was the man who knew more about it than anyone else alive. He will be sadly missed."
Boyd Clack, who co-wrote the six series of High Hopes, which Gwenlan produced at BBC Wales, said: "Gareth set the standard for the genre of situation comedy by the quality of the shows he did.
"He told me that High Hopes was the third favourite show that he'd every done. Which when you look at the shows he did - I presume Only Fools and Reginald Perrin were his favourites - was very benevolent of him."
The former producer of Only Fools and Horses, Gareth Gwenlan, has died at the age of 79.