The university is welcoming more than 2,300 first year students
Students arriving at university for the first time are to be housed temporarily in hotels and guest houses after a record surge in recruitment.
Aberystwyth University said it had about 160 more freshers than it had room for in halls of residence.
First year students are up by 364 this year and the university confessed this had "surpassed expectations".
This represents an 18% rise in numbers, compared to an average increase of 2.7% in Wales and 8.8% across the UK.
Freshers are guaranteed accommodation for the first year in Aberystwyth, but second and third year students are also given rooms in halls depending on how many newcomers apply for places.
This year the university experienced a late surge in demand for courses after much of the accommodation had been allocated, said Aberystwyth Guild of Students president, Ben Hallet.
A university spokesman said: "There are up to 160 first year students who are without accommodation for the full session in university halls of residence.
"Note that this figure does change from day to day as more students find accommodation."
Freshers are likely to end up in hotels, guest houses or privately-owned property, such as flats.
The spokesman added: "All freshers who have accommodation have been asked to arrive on Saturday.
"The university has written to all students who have not been able to arrange accommodation prior to their arrival at Aberystwyth to make their way to Penbryn (halls) from 10am onwards on Sunday, 21 September."
Ben Hallet has been in talks with university officials about the problem.
"As the intake has been low in previous years, accommodation has been offered to second and third year students," he said.
"The intake has surprised us this year, but, obviously, this comes with problems. Officials have plans to cover the deficit, though.
"First years are guaranteed accommodation, but a deadline was set. There were then a number of applications after the deadline and these students are without accommodation.
"Students could be in hotels and guest houses for up to two weeks, but it's more likely to be four or five days.
"We expect between 70 and 100 students who have places at university not to turn up so this will ease concerns."
The university said it had enjoyed an "outstanding recruitment year".
Last year, a student survey found that Aberystwyth was the UK's favourite university town.