Whether your state is in the Classic or World mode, joining an alliance can be an invaluable and enriching part of your Ars Regendi experience.

In the classic version, long standing alliances such as ATIK and Evolution contain a mix of experienced and new players and the alliance forums provide an opportunity for players to discuss strategies for improving their states' and alliance's prospects. There are also alliances set up for players of certain ideologies, such as Red Tendancy. In the worlds, alliances come and go more frequently, as players cannot re-enter a world when their reign comes to an end. Joining a world alliance can increase your chances of survival, as your allies may help you to fend off any attacks made against your state.

Alliance leaders are able to collect membership fees from each state and may redistribute these fees to any member states as they see fit. Some alliances use this facility to help states to repay their national debt more quickly or to fund projects or economic growth. For world states, payments are often made to help with the costs of being attacked by an aggressor or defending a state that's under attack. Alliances members can also vote to enact reforms that they may no be able to realise independently because of the level of regent influence required.

Alliance leaders can choose to expel members from an alliance at any time. Some of the top ranked alliances will sometimes take advantage of this option to replace incommunicative or poorly performing regents with waiting applicants, who may benefit more from alliance membership and, in turn, be a more valuable member of the alliance.

When an alliance leader dies or is deselected

, control of the alliance passes on to the vice leader. If there is no valid chain of command in an alliance when the leader's state goes exitus, then the alliance will become closed to new members as there will be nobody in charge to accept new applications. The alliance leader is always highlighted in bold in the list of alliance states. If there is no emboldened state in the member list, then your state will be unable to join the alliance. You'll still be able to submit an application, but this will sit in limbo indefinitely until you withdraw the application or reapply to a different alliance.

New alliances can be created by Premium members, or they can be purchased through use of the game's coin system.