Cabin and ground crew from four European countries have agreed to strike on July 25 and 26,, threatening to disrupt flights of low-budget airline at the height of the summer holiday season.
Unions issued a list of changes they wanted to their terms and conditions on Wednesday, including demand that all contracts at the airline be subject to local law rather than Irish law.
Unions also warned that further industrial action might follow if Ryanair refuses to improve working conditions.
Ryanair has said that its employment conditions are competitive and described demands as pointless.
Earlier this week about 100 Ryanair pilots based in Ireland announced plans to stage a walk out on July 12.
In June 2018, Dublin-headquartered Ryanair had over 1,100 flight cancellations due to air traffic control strikes and staff shortages, compared to only 41 cancellations at the same month a year ago.