A baby bottle, nursing bottle, or feeding bottle is a bottle with a teat (also called a nipple in the US) attached to it, which creates the ability to drink via suckling. It is typically used by infants and young children, or if someone cannot (without difficulty) drink from a cup, for feeding oneself or being fed. It can also be used to feed non-human mammals, whose mother cannot feed their young or mammals which have no mother.

Hard plastic is the most common material used, being transparent, light-weight, and resistant to breakage. Glass bottles have been recommended as being easier to clean, less likely to retain formula residues, and relatively chemically inert. Hybrid bottles using plastic on the outside and glass inside have also been developed. Other materials used for baby bottles include food-grade stainless steel and silicone rubber.

Baby bottles can be used to feed expressed breast milk, infant formula, or pediatric electrolyte solution. A 2020 review reports that healthy term infants, when breastfeeding or bottle-feeding, "use similar tongue and jaw movements, can create suction and sequentially use teat compression to obtain milk, with minimal differences in oxygen saturation and SSB patterns" (suck–swallow–breath patterns). Sick or pre-term babies may not be able to breastfeed or take a bottle effectively and may need specialized care.

The design characteristics of the bottle and teat have been found to affect infant feeding and milk intake. Interactions between the infant and the caregiver feeding them affect the infant's milk intake during feeding. Whether the caregiver or the infant controls the feeding appears to affect the infant's ability to learn to self-regulate their milk intake. Proper cleaning and sterilization of bottles are recommended to avoid bacterial contamination and illness, particularly in areas where water quality and sanitary conditions are not good.

A typical baby bottle typically has four components: the first is the main container or body of the bottle. A teat, or nipple, is the flexible part of the bottle that the baby will suck from, and contains a hole through which the milk will flow. The collar goes over the nipple and typically screws onto the neck of the bottle, forming a seal. Most, but not all baby bottles will also have a cap or travel cover that goes over the teat to keep it clean and to prevent small spills. Some bottles may optionally have a disposable liner.

Design concerns for the making of baby bottles often reflect safety or comfort. A safe baby bottle should not break, should not come apart easily into small or potentially harmful components, should not be made of materials that pose a health risk, and should be easy to clean so as to avoid bacterial contamination and illness.

A bottle should also be comfortable for both caregiver and baby to use. Bottles that are lightweight and easy to hold can be desired by both babies and mothers. A variety of shapes are available. The design of containers, nipples or teats may mimic the shape of the mother's breast. Designers may try to mimic the flow rate of breastfeeding: the baby should be able to get enough nourishment, but at the same time not be overwhelmed or overfed.

Over time a wide variety of materials have been used for infant feeding vessels (see History). The materials now most commonly used in baby bottle containers are glass and some types of plastics. Food-grade stainless steel and silicone rubber are also used. Each of these four materials—plastic, glass, silicone and stainless steel—has advantages and disadvantages. The standard materials used in teats/nipples are latex rubber and silicone.