"I don't think we'll open up many new lines in the UK for the next twelve or eighteen months, until this current uncertainty is removed," chief executive Michael O'Leary told AFP in Brussels.
Ryanair earns more than a quarter of its sales in Britain and is particularly at risk to turbulence from the shock vote.
O'Leary said the entirety of an upcoming delivery of 50 Boeing aircraft would be used for routes outside Britain.
O'Leary said he hoped Britain would remain in the European single market despite the shock vote on Thursday.
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"That has delivered enormous benefits for not just UK citizens but for European citizens," he said.
"But it's a matter for the UK government, whenever that government emerges," he said.
Since the June 23 referendum, British Airways owner IAG and British no-frills airline EasyJet have issued profit-warnings, as the pound dives against the euro on financial markets.
Based in eurozone-member Ireland, Ryanair would remain unaffected by the tumbling pound.
"If sterling is weaker, it means we're getting paid less. But you know, Ryanair always does well when prices are falling and fares are getting cheaper," O'Leary said.
"More people fly and they fly Ryanair," he added.