The various parties and celebrations that take place between the engagement and "I do" are all important parts of the wedding experience. But who gets invited to the different parts of wedding celebrations? This is not as complicated as it might first appear.
To start with, a general piece of advice: The bride and groom should consider who their wedding guests will be in advance of any parties. The wedding guest list doesn't need to be finalized, but the couple should have a firm idea of who they're certain to be inviting, for a simple reason: Anyone invited to any wedding party (office showers excepted) must also be invited to the wedding.
Apart from the reception, most wedding parties tend to be smaller than the full wedding guest list, since they are typically meant to be intimate get-togethers for focused groups of friends and family. Depending on the party, the invitees might be the couple's nearest and dearest, the bride's girlfriends, or just her attendants. Whatever you do, though, don't invite someone to one of these parties if they're not invited to the wedding! Asking someone to any of the lead-up celebrations for a wedding but not the wedding itself is simply rude, not to mention misleading.
Engagement parties: Guests invited to the engagement party are also customarily invited to the wedding. That might seem like a lot figure out so far ahead of time, but it can save you a lot of trouble later. People invited to an engagement party will naturally assume they're going to be invited to the wedding, and the last thing you want to do is raise any false expectations. For this reason, it's often best to limit the engagement party guest list, inviting only those you're sure will be invited to the wedding.
Showers: Close female friends and relatives of the bride, or, if it's a Jack and Jill shower, close friends and relatives of the bride and groom
Bachelorette parties: Again, close female friend and family of the bride --usually those closer to her in age, though moms and aunts have been known to make appearances. if the gather is co-ed, close friends and family of both the bride and groom are invited.
General wedding-week parties: Anyone in town, of the bride and groom's choosing.
Bridesmaids' party/groomsmen's dinner: The bride, her bridesmaids, and sometimes the mother; the groom, his groomsmen, and sometimes his dad.
Rehearsal dinner: The parents, siblings, and any other children of the bride and groom; their attendants; and the officiant. More guests, including other relatives, close friends, and out-of-town wedding guests can be invited at the discretion of the couple (and as budget allows).
Belated reception: Anyone who missed the wedding and /or any previous receptions.
Post-wedding brunch: Usually, everyone who was invited to the wedding. If you choose to invite only a select group, be discreet when extending invitations.