How do I invite a collaborator to all private repositories?

Is it possible to invite a github user to collaborate on all private repositories or do I have to invite one by one?

I ask because I don’t want to have to do this for about 40/50 private repositories and then manage them later on down the line.

If these repositories are owned by an individual account, you’ll have to invite your collaborators to each one. If you transfer your repositories into an organisation account, you can make your collaborators members of the organisation which can make managing permissions much easier in the long term.