The First Minister said there were “no words to describe this utter shambles adequately”.
Ms Truss will become the shortest serving Prime Minister in history after she battled an open revolt from Conservatives demanding her departure.
Ms Sturgeon told the BBC: “This is an almighty mess, and it’s people the length and breadth of the UK who are paying the price of this.
"I think Liz Truss’s early resignation as Prime Minister was probably inevitable the moment she walked into Downing Street.
"But Liz Truss isn’t the problem here – she’s the symptom of a much more fundamental problem. A broken Tory Party, certainly, but also a broken UK political system.
"What needs to happen now? Well, on a UK level there must be a general election. It is a democratic necessity.
"The idea that the Tories can unite behind a Prime Minister now, any Prime Minister, let alone one that is in the public interest, I think is for the birds.
"But fundamentally, the UK now needs to have a democratic choice over its next Prime Minister. There’s even ludicrous suggestions this afternoon that Boris Johnson is going to try to make a comeback.”
She added: “Of course, for Scotland that doesn’t really solve the fundamental problem, because Scotland’s votes don’t determine the outcome of UK general elections.”
Ms Sturgeon earlier tweeted: “There are no words to describe this utter shambles adequately. It’s beyond hyperbole – & parody.
“Reality tho is that ordinary people are paying the price. The interests of the Tory party should concern no-one right now. A general election is now a democratic imperative.”
Deputy First Minister John Swinney called the Conservative Party “a disgrace”, adding: “We need an election now and Scotland needs to be independent of this farce.”
Scottish Conservative leader Douglas Ross said Ms Truss had made the “right decision” by stepping down.
He said: “I wish Liz Truss and her family well. No matter where you stand on her decisions as Prime Minister, politics can be very tough on people personally.
“She has made a difficult choice, but it is the right decision. There were no other options after recent events.
“We must now move forward quickly with the election of a new leader and prime minister to restore stability for the good of the country.
“It is vital that the Conservative and Unionist Party unites and continues the hard work of getting the whole of the UK through the big challenges we face.”
Asked about calls for a general election, Mr Ross told Bauer Media: "I think people can also see that this is a Government that was elected in 2019 for up to five years. There’s still almost two years, more than two years, of that term to go.
"And the fact that there is still a significant Conservative majority, then I think actually what people will want to see is the Government getting on with stabilising things in the country, in the economy, getting their bills down, helping people, businesses and communities across Scotland and the United Kingdom.”
Mr Ross previously told the BBC the “whole optics of this are awful”, adding: “People are worried about their bills, they’re worried about their mortgages, and they expect the Government to deal with these issues, and that’s what I know the Conservative Government will be focusing on when we come back here next week.”
Speaking from a lectern in Downing Street, Ms Truss said she had told the King she was resigning as the leader of the Conservative Party as she recognised she “cannot deliver the mandate” which Tory members gave her little over six weeks ago. She held talks with the chairman of the 1922 Committee of backbench Conservatives, Sir Graham Brady, and agreed to a fresh leadership election “to be completed within the next week”.
SNP Westminster leader Ian Blackford said: "It was inevitable Liz Truss would have to go after the damage she's inflicted, but merely swapping leaders of a broken Tory Government is not enough. There must now be a general election – people will accept nothing less.
"The UK is in a state of constant crisis and long-term decline. With all the Westminster parties signed up to the economic pain of a hard Brexit and austerity cuts, it is clear independence is the only way to keep Scotland safe and escape the chaos of Westminster control for good."
Ms Truss said she would remain Prime Minister until a successor has been chosen. Her resignation came just a little over 24 hours after she told MPs she was a “fighter, not a quitter”.
Scottish Labour leader Anas Sarwar said: “It is right that Liz Truss has resigned. But, in truth, this entire Tory Government has to go. The next Tory leader will have no mandate to be Prime Minister – we need a general election now.”
Scottish Secretary Alister Jack said: “I am sorry to see the Prime Minister step down. However, she was clear that she was not able to deliver her mandate, and I respect her decision.
“What is important now is that the Conservative Party acts quickly to elect a new leader, one we can all get behind.
“The UK Government has acted swiftly to support families and businesses, to help people through the winter, in the face of very significant global challenges.
“There is much more to be done, and we need to unite and continue to deliver for people in our country.”