Some 750 doctors in 25 countries are to perform the procedure on more than 3,000 volunteers to mark World Vasectomy Day, with many operations being provided for free or at discounted rates.
"In helping to shoulder responsibility for family planning, men become heroes to their partners, to their families and to our future," said event co-founder Jonathan Stack.
The event is being held as a report from campaigners and donors warned efforts to get modern contraceptives to women in some of the world's poorest countries are not on track, with millions fewer reached than had been hoped.
The men lay on an operating table in the clinics - buses fitted out with medical equipment - while doctors performed the short procedure, which involves cutting the tubes which transport sperm from the testicles, under a local anaesthetic.
Vasectomies were also being carried out to mark the day in countries including India, the United States and Spain.
In many countries, less than one percent of men get vasectomies, despite the fact the procedure is safe and in the majority of cases has no effect on sex life, the organisers said.
In Muslim-majority Indonesia, efforts to persuade men to get vasectomies have been hampered after the country's top Islamic clerical body several years ago declared the procedure "haram", or against Islamic law.
Other attempts to encourage vasectomies have backfired. A district on Sumatra announced in 2012 it would hand out cash to civil servants who underwent the procedure - only for the move to spark anger from women who feared their sterilised husbands would have affairs.
