In the UK, hen party and stag do are the pre-wedding celebrations for the bride and groom respectively.
Organised by the maid of honour or chief bridesmaid, typically in consultation with the bride. The format ranges from quiet afternoon teas to weekends abroad. See our free hen party planning checklist.
Organised by the best man. Traditionally involving a night out; increasingly includes activities (karting, golf, escape rooms). The stereotype of extreme behaviour has faded — most modern stag dos reflect the groom's actual interests.
Some couples choose a combined sten (stag/hen) party, particularly if their friend groups overlap significantly. This is completely normal and increasingly common.
Typically 4–8 weeks before the wedding. Not too close to the wedding (the couple needs to be well-rested and focused on logistics).