A birthday cake is a cake eaten as part of a birthday celebration. While there is no standard for birthday cakes, they are typically highly decorated layer cakes covered in frosting, often featuring birthday wishes (Happy birthday) and the celebrant's name. In many cultures, it is also customary to serve the birthday cake with small lit candles on top, especially in the case of a child's birthday. Variations include cupcakes, cake pops, pastries, and tarts. In more recent years, it has become a common flavour for confectionery including ice cream, PopTarts, various cereal varieties among others. The flavour is usually vanilla with sweeter hints to imply sprinkles.

The practice of serving cake on birthdays is commonplace in many cultures. In contemporary Western cultures, birthday cakes for children are often topped with small candles, secured with special holders or simply pressed down into the cake. In the Anglosphere, the number of candles often corresponds to the age of the individual being celebrated, occasionally with one extra for luck. An increasingly popular alternative is to use candles shaped as the numeral digits of the celebrant's age. Sparklers may also be used alongside or instead of the traditional wax candles.

Birthday cakes have been a part of birthday celebrations in Western European countries since the middle of the 19th century. However, the link between cakes and birthday celebrations may date back to ancient Roman times; in classical Roman culture, cakes were occasionally served at special birthdays and at weddings. These were flat circles made from flour and nuts, leavened with yeast, and sweetened with honey.