The former Liverpool and Scotland star announced he was undergoing treatment in a post to his Instagram followers.
He said he had previously shared an "inadvertent social media post" indicating his diagnosis, blaming his "useless technology skills", and asked for privacy.
Dalglish wrote: "As my inadvertent social media post has indicated, I am currently undergoing treatment for cancer.
"Unlike my mobile phone use, the treatment is going well.
"Ideally, this would have remained private because that's the way it should be, but my useless technology skills have forced my hand.
"I did not mean to make this matter public so I would appreciate it if the privacy of my family and myself are respected.
"As ever, thank you to the wonderful medical staff who have shown incredible care and discretion, not just for me but for many, many others. They are a credit to themselves."
In a response, Liverpool FC posted a message saying: "We are all with you, Sir Kenny."
Three more recent Liverpool greats, Steven Gerrard, Robbie Fowler and Jamie Carragher, also commented on Dalglish's post, all saying they were sending their love.
Andy Robertson, who is leaving the club this summer, and former captain Jordan Henderson, posted heart emojis.
Ex-England captain and Match Of The Day pundit Alan Shearer added: "Everyone is with you, Kenny."
Sir Kenny's son Paul, a former footballer himself, wrote: "Love you Dad. You got this."
Former Liverpool players, Lucas Leiva and Sander Westerveld, responded to the post, with Leiva simply posting a series of heart emojis.
Westerveld wrote "YNWA", a reference to the Liverpool anthem You'll Never Walk Alone, which featured in many of the comments.
Dalglish scored 172 goals for Liverpool in 13 seasons as a player, winning six league titles and three European Cups during the club's glory years.
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He later took charge as manager, guiding the team to three league titles and two FA Cups in the 1980s.
He made 320 appearances for Celtic before moving to Anfield in 1977, scoring 167 goals and played 102 times for Scotland.
Dalglish was knighted in 2018 for his services to football, charity, and the city of Liverpool.
Kevin Keegan, another prolific former Liverpool forward, whom Dalglish was signed to replace, revealed on Monday that he has stage four cancer.
Craig and Lindsay Foreman were handed a 10-year prison sentence in February after being convicted of espionage, which they both deny.
The pair's family have claimed they were not permitted to attend their appeal hearing and have been left with no other options except for "starving themselves in protest".
They added that Mr Foreman is on day 25 of his hunger strike, and Ms Foreman is on day 16 of hers, adding that all communication between them has been cut off by Iranian authorities.
The couple were jailed following their arrest in January 2025 while travelling through Iran during an around-the-world trip by motorcycle.
Ms Foreman's son Joe Bennett said: "My mum Lindsay and step-dad Craig were not permitted to attend their own appeal hearing.
"We don't know if they received a proper account of what was argued on their behalf.
"We know they had been asked to sign documents in Farsi, documents they could not read, and they refused, but we don't know the details of when, or what they were.
"Their case has now passed to the Supreme Court, but we don't understand the process, the timeline, or what, if anything, will be submitted in their name."
An FCDO spokesperson said "We are disappointed by the appeal decision and will continue working to ensure that Craig and Lindsay are returned safely to the UK.
"Since their arrest last year, Britain's ambassador to Tehran, diplomats and officials in London have been working to provide consular assistance. This includes the ambassador visiting them in prison and facilitating calls with their family back in the UK."
Mr Bennett said he met with officials at the Foreign, Commonwealth and Development Office (FCDO) on Monday, but left without "clarity on what pressure is being applied to Tehran".
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He also accused the British government of being responsible for the pair's hunger strike, saying they had "run out of ways to make their own government act".
"The dial needs to shift, and it needs to shift now," he said.
The FCDO warns all British and British-Iranian nationals not to travel to Iran because of a "significant risk of arrest, questioning or detention".
The government has described the couple's 10-year sentences as "completely appalling and totally unjustifiable".
The woman, who cannot be named for legal reasons, was struck as the vehicle responded to an emergency call in Streatham, south London, in 2019.
She suffered serious head injuries and is now cared for by her family, Giles Mooney KC, for the woman, told the High Court on Tuesday
He told the court that in 2024, the two sides agreed the woman partly contributed to the collision and she would be awarded 40% of any damages.
Mr Mooney said this meant she would receive around £1.3m, which the woman and her family hoped to use to buy a property to support her care.
Judge Sylvia de Bertodano approved the settlement and said the woman spent almost six months in hospital after the collision.
"She lives now with her family, but she continues to suffer life-changing, ongoing symptoms as a result of the accident. She will never work or live independently again," she said.
The judge said the settlement was "sensible" and described the family's care as "quite outstanding", adding: "I am sure that the claimant's family are hugely relieved that this is over."
She said: "I recognise that the damages in terms of money will only be a proportion of what is needed, but I very much hope that it means that the family can move forward in the certainty of what funding is available to support her future."
The judge addressed the woman in court, saying: "I would like to wish you and all your family the very, very best for the future."
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Adam Clemens, for Scotland Yard, said: "May I just take this opportunity to wish the claimant and her family the very best of luck going forward."
Appearing at Birmingham Crown Court via video-link from HMP Brinsford, 19-year-old Omar Majed started to take off his prison-issue grey tracksuit bottoms.
Judge Andrew Smith KC then cut short his remarks to Majed and stated for the record that prison staff had escorted the defendant out of the video hearing room.
The judge was trying to address Majed to let him know when he next needed to appear before the court, which heard he was not arraigned during the hearing due to the need for psychiatric reports.
A further case management hearing for Majed is now set for 27 July. A provisional date for a trial, lasting two weeks, was also scheduled for 3 November.
Thousands of fans had to leave Birmingham's Utilita Arena and Kay, 52, was ushered off stage about 45 minutes into the performance on 1 May after the teenager allegedly "barged" his way into the venue without a ticket in May, Birmingham Magistrates' Court previously heard.
Majed indicated to a police officer and others that a bomb may have been left at the venue, prosecutor Ros Buttler said.
She said the alleged hoax had "serious repercussions", as around 13,000 people were expected at the gig, which had to be cancelled.
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Footage from the performance showed crowds filing out of the arena, which can seat 15,800 spectators.
Majed, of Saltley, Birmingham, was charged with allegedly making false communications that a bomb was present in the arena.
He was previously removed from court during his first appearance on 4 May, after he was repeatedly talking during a hearing.
Abdullah Hayayei, 36, who represented the United Arab Emirates, was killed at Newham Leisure Centre, east London, during a practice session in 2017.
The father-of-five was preparing to represent his country in the F34 class discus, javelin and shot put at the World Para Athletics Championships in London when part of a 31st throwing cage fell on him.
He was left with a severe head injury after the 5ft high cage toppled over because it was put up incorrectly and without its base plate, in an "accident waiting to happen", a court was told.
The national governing body for athletics was charged with causing the death of Mr Hayayei by "supplying for use... a discus/shot put cage which it used and operated without its base structure and which collapsed" into the Paralympian while he was practising shot putting.
In February, UK Athletics Ltd admitted corporate manslaughter at the Old Bailey, having previously denied the charge.
On Tuesday the firm was ordered to pay nearly £400,000 over six years - made up of a fine of £350,000 and legal costs of £44,000, as well as a statutory surcharge.
Keith Davies, who was the head of sport for the 2017 World Para Athletics Championships, also pleaded guilty to a health and safety charge.
The 79-year-old was handed a community order to do 175 hours of unpaid work, to be carried out in the next 12 months.
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Sentencing, Judge Richard Marks KC said Mr Hayayei's death was "tragic, untimely and wholly avoidable".
He noted failings by UK Athletics were not a "one-off" but said any financial penalty would "weaken" its ability to support individual athletes and athletics in the community.
He told Davies, a retired PE teacher, that he knew, or ought to have known, base plates were an "integral part" of the cage construction.
He was "on notice" following an earlier collapse of an identical cage, the judge said, adding: "This was an accident which sooner or later was waiting to happen."
In the five years since UK Athletics acquired two identical cages originally used in the 2012 Olympics, they had never been properly assembled with the base plates attached, the court heard.
Davies had claimed UK Athletics had never been supplied with base plates, but this proved not to be true, the court was told.
In a statement, UK Athletics said: "Today's sentence marks a significant moment for UK Athletics. The failings identified in this case should never have happened, and UK Athletics is deeply and genuinely sorry for what occurred and for the impact it has had on all those affected.
"Since then, substantial changes have been made to strengthen the way safety, governance and event operations are managed across the sport. While nothing can undo what happened, there has been a determined focus on learning from these events and ensuring stronger standards and safeguards are in place throughout athletics."
Detective Chief Inspector Lucie Card of Scotland Yard said: "Abdullah was a talented athlete whose life was cruelly cut short by the failings by those who were meant to keep him safe.
"The lead technician of the firm that had manufactured the throwing cage knew within seconds of seeing the scene that the equipment hadn't been erected properly.
"Our investigation demonstrated that for years, the cage, which was donated to UK Athletics after the 2012 Olympics, wasn't being properly secured by UK Athletics and its representatives."
Mr Hayayei had cerebral palsy and had been due to compete in the para athletics shot-put event during the World Athletics Championships in Stratford, the court heard. He had five children aged between two and 14 when they lost their father.