Megastar Amitabh Bachchan, who had visited the ailing politician at his residence 'Matoshree' recently, said it is hard to believe that Thackeray is no more.
"I sat by his bedside for hours these past few days, a prayer in my heart, watching him struggling to breathe, but fighting. Each day he continued his struggle with a grit that was baffling even for the doctors on hand.
"And just a couple of hours back, as I stand next to his still, peaceful, saffron draped body, it is difficult to imagine that he has left us!," Bachchan, 70, tweeted.
Melody queen Lata Mangeshkar said Maharashra was "orphaned" by Thackeray's death at the age of 86.
"Hindu hridaysamrat, param adarniya Shri Balasaheb Thackeray hum logon ko chhodke anant mein vileen ho gaye. Yeh satya hai ki aaj Maharashtra anaath ho gaya. (The king of Hindu hearts, Shri Balasaheb Thakeray left us for eternity. It is true that Maharashtra is orphaned today)," she said.
Actor-producer Ajay Devgn said, "A man of convictions and a man of vision. A great leader. Rest in peace Balasaheb."
Director Ram Gopal Varma, whose Bachchan starrer Sarkar was loosely based on Thackeray's life, tweeted, "...can't ever forget the hug the real Sarkar gave me when he saw reel Sarkar... Bala saab was a true epitome of power in every sense of the word."
Bollywood actor Akshay Kumar on Twitter: "His demise has left a deep void in Indian politics,always admired him for his courage,The real Tiger. May strength be with his family. RIP BalaSaheb Thackeray."
Veteran actor Anupam Kher on Twitter: "Just woke up in NY to d sad news about BalaSaheb. He'll always remain larger than life. He was helpful, Courageous & a true Nationalist. RIP."
Twitter was flooded with messages as celebrities took to the micro-blogging website to condole Thackeray's death.
Filmmaker Madhur Bhandarkar tweeted, "He lived with great conviction in his believes, which led him to be a great leader. Wish strength to his family! Balasaaheb was outspoken and sharp observer. He will deeply be missed."
Arjun Rampal wrote, "RIP Balasaheb, condolences to his family. Peace be with you and all your loved ones."
Actor Riteish Deshmukh, who lost his politician father Vilasrao Deshmukh recently, also joined in to pay his last respect to the Shiv Sena supremo.
"RIP - Saheb. Balasaheb was a Hero- people- Loved him, Copied him, Followed him," Deshmukh said.
Director Karan Johar wrote, "Thoughts and prayers with the Thackeray family....RIP balasaab."
Mahesh Bhatt tweeted, "Our dead are never dead to us, until we have forgotten them. The memory of Bal Thackeray will live in the memory of we Mubaikars forever."
Actor Vivek Oberoi wrote, "RIP Balasaheb --- The Roaring Tiger of Maharashtra! Our prayers are with the Thackeray family and the millions of followers."