Opinion - What could happen next now the UK Prime Minister's Brexit deal has been rejected and her government has survived a vote of no-confidence.
Mrs May will return to Parliament on Monday to make another statement.
With the clock ticking down to Brexit on 29 March, what are the options?
1. No deal
If nothing else happens, the default position would be a no-deal Brexit. The law is already in place which means the UK will leave the EU on 29 March 2019. And, in any case, EU rules mean the UK would leave then.
The government would probably want to pass some legislation to prepare for no-deal but that's not strictly essential.
MPs unhappy with the prospect of a no-deal Brexit defeated the government on 8 January - voting to limit the Treasury's ability to raise certain taxes. The move is being seen as symbolic - as the government could probably find another way to raise money - but it is an indication that MPs will try to stop no deal.
Read more on Brexit:
- Theresa May survives no confidence vote
- MPs vote down Theresa May's deal
- UK Labour's Jeremy Corbyn demands election over Brexit deadlock
2. Second vote for MPs
The government could broadly stick with the current deal.
Following the no confidence vote Mrs May talked to opposition party leaders, though Labour did not take part, and said meetings would take place between senior government representatives and groups of MPs about how to deliver the Brexit plan.
It could involve making some small adjustments and possibly requesting minor changes, from the EU, to the deal. Or making promises about how negotiations on the future relationship will proceed after Britain has left the EU.
Either way, the plan would be to have another vote in Parliament soon.
If the government comes back with exactly the same deal it could run into a problem. There's a general principle that MPs shouldn't be asked to consider the same question twice in a single session.
However, it's been argued that this rule would not apply if the will of Parliament had changed. And, in any case, the Speaker could choose to allow a second debate to proceed.
3. Major renegotiation
With MPs having voted against the deal, the government could propose to negotiate a new Brexit deal.
This would not be a question of carrying out minor tweaks and having a second vote.
Instead, there could be a complete renegotiation that would take some time and might well require an extension of Article 50 to delay Brexit.
This would require two key steps. First, the UK would have to make a request to the EU for an extension. This could be granted but only if all EU countries agree at a vote of the EU Council.
Second, the government would have to table a statutory instrument to change the definition of "exit day" in the EU Withdrawal Act. MPs would get a chance to vote on this change.
If the EU refused to re-enter negotiations, the government would have to plump for one of the other options instead.
4. Another referendum
The government could instead choose to have another referendum.
As with a renegotiation or early election, this might well require an extension to Article 50. It's already too late to hold a referendum before 29 March.
And it can't just happen automatically. The rules for referendums are set out in a law called the Political Parties, Elections and Referendums Act 2000.
There would have to be a new piece of legislation to make a referendum happen and to determine the rules, such as who would be allowed to vote.
It couldn't be rushed through because there has to be time for the Electoral Commission to consider and advise on the referendum question.
The question is then defined in the legislation.
Once the legislation has been passed the referendum couldn't happen immediately either. There would have to be a statutory "referendum period" before the vote takes place.
Experts at University College London's Constitution Unit suggest that the minimum time for all of the required steps above is about 22 weeks.
Even if that could be shortened a little, it would still take us well beyond the end of March.
5. Call a general election
Mrs May could decide that the best way out of the deadlock would be to hold an early general election in order to get a political mandate for her deal.
She doesn't have the power just to call an election. But, as in 2017, she could ask MPs to vote for an early election under the terms of the Fixed Term Parliaments Act.
Two-thirds of all MPs would need to support the move. The earliest date for the election would be 25 working days later but it could be after that - the prime minister would choose the precise date.
As with the "renegotiate" plan, this course of action could also involve a request to the EU to extend Article 50.
- David Townsend: "Enter self-preservation, a guiding principle in the Conservative Party"
6. Another no confidence vote
Labour could table another motion of no confidence in the government at any time.
Under the Fixed Term Parliaments Act 2011, UK general elections are only supposed to happen every five years. The next one is due in 2022. But a vote of no confidence lets MPs vote on whether they want the government to continue. The motion must be worded: "That this House has no confidence in Her Majesty's Government."
If a majority of MPs vote for the motion then it starts a 14-day countdown. If during that time the current government or any other alternative government cannot win a new vote of confidence, then an early general election would be called.
That election cannot happen for at least 25 working days.
6. Other possibilities
The European Court of Justice has ruled that it would be legal for the UK to unilaterally revoke Article 50 to cancel Brexit (without the need for agreement from the other 27 EU countries).
With the government still committed to Brexit, it's very likely that a major event such as a further referendum or change of government would have to happen before such a move.
After Mrs May survived a challenge to her leadership, the Conservative Party's rules mean she won't face another for 12 months.
But she could always decide to resign anyway, if she can't get her deal through and she's not prepared to change course.
That would trigger a Conservative leadership campaign which would result in the appointment of a new prime minister.
She might also come under pressure to resign if MPs pass a "censure motion" - that would be a bit like a no confidence vote but without the same automatic consequences. Again this could lead to a change in prime minister or even a change in government.
Whoever ended up in charge would still face the same basic range of Brexit options though.