Ang ku kueh (Chinese: 紅龜粿; Pe̍h-ōe-jī: Âng-ku-kóe; Tâi-lô: Âng-ku-kué; Teochew Peng'im: ang⁵ gu¹ guê²), also known as red tortoise cake, is a small round or oval-shaped Chinese sweet dumpling with soft, sticky glutinous rice flour skin wrapped around a sweet central filling. It is molded to resemble a tortoise shell and is presented resting on a square piece of banana leaf. As suggested by its name, red tortoise cakes are traditionally red in color and has a sticky, chewy texture when eaten. Red tortoise cakes are shaped like tortoise shells because the Chinese traditionally believed that eating tortoises would bring longevity, good fortune and prosperity. Considered to be auspicious items, these sweet pastries are especially prepared during important festivals such as Chinese New Year as offerings to the Chinese deities.

Red tortoise cakes are also prepared for occasions that are culturally important to the Chinese such as a newborn baby's first month or birthdays of the elderly. Eating red tortoise cakes during these times is meant to represent blessings for the child and longevity for the elderly. Aside from China, in modern times, red tortoise cakes continue to be important food items during Chinese festivals in many countries with significant Sinophone communities especially in Southeast Asia. However, eating red tortoise cakes in these countries is no longer restricted to special occasions for red tortoise cakes are also commercially available in many pastry shops and bakeries.

There are two main components in red tortoise cakes: skin and filling. The skin is made mostly from glutinous rice flour and sweet potato whereas the fillings are made from precooked ingredients such as mung bean or ground peanuts and sugar. After kneading and molding the ingredients together, the red tortoise cakes are steamed on a piece of banana leaf. In countries such as Singapore, these pastries are popular snack items and are especially popular with children because of their sweet and savory taste. In fact, many bakeries in Singapore have created red tortoise cakes in a variety of assorted flavors, including jelly and red bean, to cater to all tastes and preferences. In Vietnam, ang ku kueh was called bánh Quy, it is sold in almost every Chinese market, especially in Ho Chi Minh City (Cho Lon area). The word "quy" (龜) is the Sino-Vietnamese word for "tortoise."

In Chinese culture, the color red is traditionally used as a symbol of joy and happiness whereas the tortoise symbolizes longevity, power and tenacity. As such, red tortoise cakes are of high cultural significance and value among Chinese people. They are typically associated with auspicious occasions and are especially prepared during birthdays and religious festivals to symbolize blessings and good fortune.

Chinese New Year is the most important festival in Chinese culture as it represents the start of a new year for everyone where people could reconcile and welcome the new year in hope for peace and prosperity. During this festival, the Chinese people would pray for good fortune and sweets such as rice cakes and red tortoise cakes are offered to the Chinese deities on ritual altars. These ritual offerings are made in the hope that the sweetness from these cakes will leave a sweet taste in the mouths of the deities and they will bless the people with a prosperous year ahead.

The Jade Emperor is one of the most important gods in Chinese folklore. He is believed to be the ruler of heaven and his birthday falls on the ninth day of the first lunar month. To celebrate his birthday, the Chinese people will conduct prayers in his name and prepare food within Chinese temples or Chinese households as ritual offerings. In Chinese culture, red tortoise cakes are considered must-haves among food items offered to the Jade Emperor on altar tables.

Because the number 6 is considered an auspicious number in Chinese culture, red tortoise cakes are placed on the altar table in multiples of six such as 12, 24 or 36 in the hope that he will bless the people with good fortune and prosperity.

Qing Ming Festival is the time for the Chinese to visit the burial grounds of their ancestors to pay their respects. Prayers are conducted to honor the ancestors and food items such as red tortoise cakes are prepared as offerings. However, there is some difference in the red tortoise cakes that are prepared for this occasion. Apart from the usual red tortoise cakes that are prepared in the color red, there are separate red tortoise cakes that are prepared in the colors green or white. The reason for these differences in color between red tortoise cakes is that these colors are of cultural significance to the Chinese people. The color red is representative of the virtuous life led by the ancestors whereas the colors green and white embody the descendants' grief and their hope that their ancestors are coping well in the afterlife.