In common law, battery is a tort falling under the umbrella term 'trespass to the person'. Entailing unlawful contact which is directed and intentional, or reckless (or, in Australia, negligently) and voluntarily bringing about a harmful or offensive contact with a person or to something closely associated with them, such as a bag or purse, without legal consent.

Unlike assault, in which the fear of imminent contact may support a civil claim, battery involves an actual contact. The contact can be by one person (the tortfeasor) of another (the victim), with or without a weapon, or the contact may be by an object brought about by the tortfeasor. For example, the intentional driving of a car into contact with another person, or the intentional striking of a person with a thrown rock, is a battery.

Unlike criminal law, which recognizes degrees of various crimes involving physical contact, there is but a single tort of battery. Lightly flicking a person's ear is battery, as is severely beating someone with a tire iron. Neither is there a separate tort for a battery of a sexual nature. However, a jury hearing a battery case is free to assess higher damages for a battery in which the contact was particularly offensive or harmful.

Since it is practically impossible to avoid physical contact with others during everyday activities, everyone is presumed to consent to a certain amount of physical contact with others, such as when one person unavoidably brushes or bumps against another in a crowded lift, passage or stairway. However, physical contact may not be deemed consented to if the acts that cause harm are prohibited acts.

Battery is a form of trespass to the person and as such no actual damage (e.g. injury) needs to be proved. Only proof of contact (with the appropriate level of intention or negligence) needs to be made. An attempt to commit a battery, but without making actual contact, may constitute a tort of assault. The tort of battery developed out of a general judicial respect of an individual's autonomy and right not to be interfered with.

Battery need not require body-to-body contact. Touching an object "intimately connected", to a person (such as an object they are holding) can also be battery. Furthermore, a contact may constitute a battery even if there is a delay between the defendant's act and the contact to the plaintiff's injury. For example, where a person who digs a pit with the intent that another will fall into it later, or where a person who mixes something offensive in food that they know another will eat, has committed a battery against that other when the other does in fact fall into the pit or eats the offensive matter.

The character of intent in civil battery is different from that for criminal battery. The character of intent sufficient for battery also varies between common law countries, and often within differing jurisdictions of those countries. In Australia, negligence in an action is sufficient to establish intent. In the United States, intention to do an act that ultimately results in contact that is either harmful or offensive is sufficient for the tort of battery, while intention to inflict an injury on another is required for criminal battery. In the U.S., courts are split on how to test for sufficient intent. Some courts use the single intent rule which seeks to determine whether or not the defendant intended to touch the plaintiff, while some courts use the dual intent rule which seeks to determine whether or not the defendant sought to harm or offend by touching.

Additionally, courts also follow the transferred intent doctrine in battery claims. For instance, if a person swings to hit one person and instead misses and hits another, they can still be held liable for a battery. Intent to commit a different tort can transfer in the same way. If a person throws a rock towards one person intending only to scare them (but not to hit them), they will be liable for battery to a different person who is hit by that rock. In the United States, critics of this doctrine believe that the tort of negligence has superseded the need for transferred intent. One issue is that the statute of limitations can be shorter for intentional torts such as battery than the statutes of limitations for negligent torts.