The UK's largest insurer will allow all new parents the same amount of paid leave after the arrival of a child.
Aviva will offer its 16,000 employees 26 weeks leave on full basic pay, regardless of their gender or sexual orientation.
The policy applies to parents who have given birth, adopted or chosen surrogacy.
But the industry body for personnel managers, the CIPD, said men's take-up of shared parental leave remained low.
Nevertheless, the CIPD said Aviva's move was a significant and positive step.
What are your rights?
- Most employed mothers are entitled to 52 weeks' maternity leave
- Statutory maternity pay covers the first 39 weeks. It is usually paid at 90% of the mother's weekly wage for the first six weeks, with the remaining 33 weeks at £140.98 a week or 90% of their weekly wage, whichever is lower
- Employees may be entitled to shared parental leave within the first year of a child's birth or adoption
- Women who earn less than £112 a week are not eligible for statutory maternity pay; instead most can claim maternity allowance
- Fathers may be entitled to one or two weeks paid paternity leave
The move tackles one of the barriers to career progression, Aviva says.
Aviva argues the move will create a "level playing field for men and women" who want to take time out of their career to spend time with their family.
The CIPD's spokeswoman welcomed Aviva's move increase the pay available "to allow both parents to play an equal part in the upbringing of their child".
Aviva would need to use male role models to show it is acceptable to take up the offer of parental leave, "to encourage a change in perceptions and foster a cultural change. Otherwise, male employees may still be reticent about taking time off, even if paid," she added.
Fathers often take a minimum amount of time off for financial reasons, whilst their partner's income is reduced.
The UK's provision for new mothers is among the worst in Europe, the TUC said earlier this year.
The trade union body says only Ireland and Slovakia have worse "decently paid" entitlements, which it defines as two-thirds of a woman's salary - or more than £840 a month.
Croatia offers six months leave; Poland, Hungary and the Czech Republic have more than four months; Estonia, Italy, Spain, Belgium, Denmark, France, Malta, and Switzerland offer more than three months.
Aviva will offer nearly double the EU minimum requirement of 14 weeks, by giving 26 weeks leave at full basic pay for each parent within 12 months of a child's arrival.
Aviva's new policy was devised by Sarah Morris, its chief people officer and a member of the company's executive committee.
She is also on the steering committee of the 30% Club, which campaigns for greater representation of women on the boards of Britain's biggest companies.
The insurer's policy is not the most generous in the corporate world, however. In August 2015 Netflix announced an unlimited leave policy allowing new parents to take as much time off as they want during the first year with their new child.