More than 72 per cent of Swiss have voted in favour of legalising abortion, bringing laws into line with most of Europe.
The result means abortion will now be permitted within the first 12 weeks of pregnancy, harmonising the legislation with current practice, which effectively allows abortion on demand.
Until now Switzerland has had some of the most restrictive abortion laws in Europe - despite loopholes in the law - along with the Irish Republic, Poland and Portugal.
"This is a great victory for women in Switzerland," said Anne-Marie Rey, a leading Swiss expert and campaigner for abortion. She added that Swiss women would no longer "feel criminalised" for terminating a pregnancy.
Sunday's vote means the Swiss have finally caught up with countries like France and Italy, which introduced liberal abortion laws in the 1970s. Germany and Austria also allow the practice, although counselling is mandatory before a woman can have a termination.
A counter-proposal to tighten Switzerland's 1942 law, which banned the practice unless a women's health was at risk, was thrown out by 82 per cent of voters. That initiative - "For Mother and Child" - would have prohibited abortion even in cases of rape.
Voter turnout was just over 40 per cent.
In reality, Sunday's vote will lead to little change in most of the country, except to simplify the process of securing an abortion. The new legislation comes into force on October 1.
"It's more for the women and also for the people responsible for doing the procedure to have a clear legal situation and to leave behind this state of uncertainty which has been there for so many years," said Professor Henning Schneider, director of obstetrics and gynaecology at Bern's University Clinic.
Loopholes in the existing law, which prohibits terminations unless a woman's health is in danger, have long enabled women to have abortions - currently between 12,000 and 13,000 terminations take place every year. That accounts for about one in every eight pregnancies.
Until now, regional health authorities have been free to decide how to interpret the law. Any licensed doctor can carry out, or approve, an abortion if he or she believes that a pregnancy would put a women's health - including mental health - in danger.
No woman has been convicted for an abortion-related offence since 1988, and only five physicians have been convicted for ignoring the abortion laws in the past nine years.
Sea change in Catholic attitudes
Analysts say Sunday's vote points to a sea change in attitudes among Switzerland's Catholics.
"I think there has been a great change in public opinion concerning everything to do with sexuality, with women's role in society and, of course, abortion," said Anne-Marie Rey. "It is now accepted that people have the right to decide for themselves things that concern their private life."
On Sunday, most of the country's Catholic cantons voted in favour of legalising abortion, with only Valais in the south and the tiny central canton of Appenzell Inner Rhodes voting against. In previous votes, Catholic cantons rejected any loosening of the law.
For some cantons - such as predominately Catholic Nidwalden - the vote means they will now have to start offering abortions in their own hospitals, rather than sending pregnant women to neighbouring cantons for abortions.
Reacting to Sunday's vote, the Swiss justice minister, Ruth Metzler, said she was surprised by the clear margin of the result. She underlined the importance of ensuring that women in difficult situations had access to advice and support.
Interior Minister Ruth Dreifuss called on the cantons to establish more counselling centres for women.
Opponents of abortion said they were dismayed by the result. The country's main pro-life group, Swiss Aid for Mother and Child, wanted to see an outright ban on abortion introduced, even where the pregnancy is the result of rape.
"We are extremely disappointed," said the organisation's Barbara Güpfert. "The unborn child will no longer be protected and women in a distressful situation will be on their own."
Sunday's ballot was the fourth vote on abortion in Switzerland since 1977. All previous attempts to either tighten or ease regulations on a nationwide level have failed to win a majority.
Switzerland's abortion rate is among the lowest of any developed country. Nearly half of all abortions are carried out on women over the age of 30, while teenage pregnancies account for about ten per cent of terminations.