"Cheap" is really two things: the cost of getting there and sleeping (flights and hotels), and the cost of being there (food, drinks, transport, sights). The cities below win on both. For each, the move is the same, go in shoulder season, mid-week, and build the trip to a budget so you can see the all-in number before you commit.
Cheap flights, cheap hotels and famously low prices once you land make Kraków the best-value break going. The medieval old town is one of Europe's prettiest, the history is extraordinary, and a sit-down meal with a drink costs a fraction of what it would in Paris. Ideal for a first international trip on a tight budget.
Spires, bridges, beer cheaper than water, and a compact centre you can walk end to end. Prague delivers a proper European city break for not much money, and the autumn light festival makes October a great time to go.
Lisbon is the mildest of the budget picks, trams, tiles and pastéis de nata over seven sunlit hills, and noticeably cheaper than Spain's big two in the shoulder months. Brilliant food for the price, and a short flight from the UK.
The paella capital has the sun and the architecture of a big Spanish city at lower prices, with fewer crowds. Valencia is a smart swap if Barcelona looks pricey for your dates.
If you want a quick hop with no early flight, Dublin and Amsterdam are short and easy. For a no-flight UK break, the Edinburgh and Bath guides cover the best-value staycations. And if it's sun you're after at the cheapest moment, see our guide to the cheapest months to travel.
What's the cheapest city break from the UK? Kraków and Prague, cheap to reach and cheap to enjoy.
Cheapest for mild weather? Lisbon and Valencia in the shoulder months.