Father-of-two Greg Gilbert, 39, from Southampton, has been diagnosed with stage four bowel cancer.
His fiancée Stacey Heale said his only chance of survival was to go abroad for treatment which she said was not available to him on the NHS.
GoFundMe said the appeal was one of the "fastest ever" campaigns on its site.
More than 4,000 people have so far donated to the fundraising page, posted at 10:30 GMT on Wednesday, including music stars Craig David and Ellie Goulding.
In a Facebook post, Mr Gilbert said the response was " truly humbling".
"I can't begin to express our gratitude - not a penny is being taken for granted and we've been moved to tears many times over the last few days reading the supportive messages from not only friends and family but also strangers from all over the world."
Ms Heale said she and Mr Gilbert had been "in tears and holding hands" as they watched the pledges come in.
She said: "It's been overwhelming; our phone has been ringing off the hook. I was refreshing the page this morning and were just like, 'oh my God, we've done it'.
"Grateful doesn't cover it. We've had one person donate £2,000. After such a difficult year for people, to have this at Christmas is so hopeful for us."
Ms Heale said she was researching options for treatment, including personalised immunotherapy in Germany and the USA.
She said she was considering posting a new fundraising target of £250,000, after a private specialist warned that Mr Gilbert's medical bills could amount to £100,000 a year.
Writing on the funding page, Ms Heale said her fiancée had begun chemotherapy for the cancer, which had spread to his lungs.
She said she was disappointed the drug Avastin, for advanced bowel cancers, was currently not routinely available on the NHS.
A fundraising gig has been organised on 5 January at the Southampton venue, the Joiners, where Delays have played many times during their career.
The band was formed in Southampton in 2001 by brothers Greg and Aaron Gilbert with Colin Fox and Rowly.

Arvind Kejriwal blamed Prime Minister Narendra Modi for the "raid", calling him a "coward and a psychopath".
"When Modi couldn't handle me politically, he resorts to this cowardice," he added.
Officials from the Central Bureau of Investigation (CBI) have denied the allegations.
"It is not a raid on Arvind Kejriwal's office, it was a raid on Rajender Kumar, principal secretary to the CM [chief minister]," CBI spokesperson Devpreet Singh told BBC Hindi.
However, Mr Kejriwal has accused the CBI of "lying".
India's Finance Minister Arun Jaitley told the upper house of parliament that the "raid has nothing to do with Mr Kejriwal".
Parliamentary Affairs Minister Venkaiah Naidu added that it had become a "fashion" for Mr Kejriwal to blame the prime minister.
Mr Kejriwal's local government has been locked in a tussle for power with the federal government since he was elected to power in February.
Unlike in much of India, Delhi's Aam Aadmi Party (AAP)-run local government does not have absolute administrative powers over the state. Control of the state's police force, land, and law and order rests with the BJP-controlled federal government.
The AAP has consistently campaigned for greater autonomy for the state, and its tenure has been peppered with confrontations.
Party members have tweeted, calling it the "darkest day in democracy".
An appeal to pay for cancer treatment for the lead singer of indie band Delays has reached its £100,000 target in 48 hours.
[NEXT_CONCEPT]
The chief minister of India's capital, Delhi, has alleged that his office has been raided by the country's federal investigation agency.