Mas said the referendum date was set almost a year away so as to give ample time for negotiations with Madrid on "the way to stage the consultation legally."
Polls indicate that Catalans are roughly evenly split on independence. The European Union and NATO have warned Catalonia it would be excluded if it seceded.
Scotland is staging an independence referendum next year, on Sept. 18. That vote has been approved by the British government.
Mas began pushing for a referendum after he failed to clinch a better financial pact for Catalonia with the central government in 2012. The referendum proposal got the support of some 1 million people who turned out at two demonstrations held since then.
The possibility of a region having the right to decide its future has stirred much political debate and raised questions as to whether it is time to reform the 1978 Constitution to ease territorial discontent. The Basque region, which has traditionally sought greater powers, failed in a bid to hold a self-determination referendum several years ago.
Catalonia is one of the country's most powerful regions and represents roughly a fifth of Spain's 1.1 trillion euro ($1.5 trillion) GDP. Its population of 7.5 million is greater than those of EU members such as Denmark, Ireland or Finland.
The region, like others in Spain, has its own language as well as Spanish. Its financial powers include some tax collecting rights.
Spain has 17 regions, each with substantial autonomy but with no control over key areas such as defense, foreign affairs, ports and airports, and in the making of national economic and financial decisions.