MacLennan passed away in the early hours of the morning. He had been suffering from Motor Neurone Disease for the past year.
He was a major figure in the Scottish theatre scene for more than forty years. One of the founding figures of 7:84 Theatre Company, he went on to establish Wildcat Theatre. Read a final interview with The Herald
In the past 10 years he has developed the Play, Pie and a Pint lunchtime theatre event. A BBC TV special programme about the series at Glasgow's Oran Mor will go ahead tonight. Read our feature on the BBC show here
MacLennan's reputation in the acting world was such that he was able to attract major talent in the form of Robbie Coltrane, Bill Paterson and Elaine C. Smith to his basement theatre in the West End of Glasgow.
MacLennan was married to actress Juliet Cadzow. His sister, Elizabeth, and her husband, John McGrath, were also co-founding members of the theatre company, which pioneered some of the most radical political drama ever seen in Scotland and the UK.
Earlier this year MacLennan spoke to The Herald about his hopes for Scotland to remain in the UK and wrote a poem about the indyref.
The arts community has today been paying tribute to MacLennan.
Alan Cumming tweeted: "RIP David Maclennan, a great man of the Scottish theatre."
Playwright, novelist and performer Alan Bissett said: "David Maclennan has died. Titanic figure at the heart of Scottish theatre. A dreadful loss. Much love to his family."
Actor Colin McCredie tweeted: "The saddest news ever. Can't believe we've lost this giant of Scottish Theatre. David MacLennan a true inspiration & a wonderful man.
"After getting boot fae Taggart, first person to offer me a job was David MacLennan and it was a joy to wear stockings & high heels for him!!"
Forbes Masson said: "RIP David McLennan. my school took me to Dummies by Wildcat in 1979. opened my eyes to politics and was one of the reasons I became an actor."
Actor John McLarnon, who is currently appearing in a stage version of The Commitments, said: "RIP David Maclennan. Honoured to have performed his work at his doctorate ceremony. A true pioneer of Scottish theatre!"
Playwright Kris Haddow tweeted: "Terribly sad to hear David MacLennan has left us. But what a phenomenal artistic legacy he leaves. He'll be with us for always."
Omar Raza, who appeared in The Limmy Show and Fags, Mags and Bags, said: "RIP to David MacLennan. A man who gave many a great platform. Saddened I won't be able to share my play with him. Love & prayers to him x"
River City actor Colin Little tweeted: "Very sad news about David Maclennan, only met him a couple of times but he was an absolute gent and a class act. RIP."
Paul James Corrigan said: "Mourning a genius... Thanks for all the laughs.. The classic cuts. And indeed the right good swally sessions. Shine on David MacLennan. X"
Sean Biggerstaff, who appeared in the Harry Potter films, tweeted: "RIP Dave MacLennan. Top man. I only wish I'd had the chance to know him better."