The primary grounds of acquisition of citizenship under ordinary naturalisation is a certain period of residence in the country The minimum period of residence required for ordinary naturalisation in EU countries ranges from 3 to 10 years. Certain types of residence (permanent, continuous, etc.) may count for naturalisation purposes. Some countries require you to hold permanent residence, pass civic and language test, before naturalising application is submitted. Poland has the lowest naturalisation period (3 years) based on residence offering the fastest citizenship path among all the other EU countries.

Here is the list of EU countries and naturalisation period.

EU state
Naturalization (Residence time)
Poland 3 years
Belgium 5 years
Bulgaria 5 years
Cyprus 5 years
Czechia 5 years
Finland 5 years
France 5 years
Ireland 5 years
Latvia 5 years
Malta 5 years
Netherlands 5 years
Sweden 5 years
Portugal 6 years
Greece 7 years
Luxembourg 7 years
Croatia 8 years
Estonia 8 years
Germany 8 years
Hungary 8 years
Romania 8 years
Slovakia 8 years
Denmark 9 years
Austria 10 years
Italy 10 years
Lithuania 10 years
Slovenia 10 years
Spain 10 years

Source: Data from European Commission Study