Students across the UK face disruption as lecturers and support staff in 60 universities start an eight-day strike.
Members of the University and Colleges Union (UCU) are taking action in two separate disputes, one on pensions and one on pay and conditions.
The strikes will affect almost half of all UK universities.
The universities say strikes are not the way forward and promise to do all they can to minimise the impact of industrial action on students.
In addition to striking, union members will begin other forms of industrial action when they return to work, including working strictly to contract, not covering for absent colleagues and refusing to reschedule lectures lost during the strikes.
This latest action follows strikes in February and March last year, meaning some students are being affected for the second time.
Staff taking action will walk out between 25 November and 4 December and the union has not ruled out further action next term.
UCU says staff have reached “breaking point” over a number of issues, including workloads, real-terms cuts in pay, a 15% gender pay gap and changes to pensions for staff in the Universities Superannuation Scheme (USS), which the union says will leave members paying in more and receiving less in retirement.
UCU general secretary Jo Grady said about 43,600 members would be taking strike action for “systemic change”.
Ms Grady said the higher education sector had “made a lot of money over the past 10 years” but that spending on staff in that period had gone down and that there had been “an attack on working conditions in the sector”.
The UCU is angry that members are now having to pay 9.6% in pension contributions, up from 8% and wants universities to pay the full increase instead.
The union estimates that, overall, changes to the pension could leave lecturers about £240,000 worse off in retirement, rising to £730,000 for professors.
But the University and Colleges Employers Association and Universities UK say employers have increased their pension contributions from 18% to 21.1% of salary, paying in an extra £250m each year.
The employers say even increasing their contributions to 22.7% of salary would cost them £373m a year.
