Ethel M Botanical Cactus Garden, Desert botanical garden in Henderson, Nevada.

Ethel M Botanical Cactus Garden covers 3 acres (1.2 ha) beside the Ethel M Chocolates factory at 2 Cactus Garden Drive in Henderson. It holds more than 300 cactus and desert plant species, over half native to the southwestern United States, with the rest from Australia and South America. Plantings include saguaro, ocotillo, teddy bear cholla and barrel cacti.

Forrest Mars Sr. retired from Mars Inc. in 1973 and began planning a candy venture named after his mother, Ethel Gale Mars, who had moved with him to the Las Vegas Valley in 1975 and died there in April 1980 aged 97. The factory opened in Henderson in March 1981, and the cactus garden followed in September 1981, averaging 300 to 400 visitors a day in its early years.

The garden takes its name from Ethel Gale Mars, Forrest Mars Sr.'s mother, who moved to the Las Vegas Valley in 1975 and died in April 1980 at 97, before the factory opened in March 1981. Since 1994 the cactus garden has been strung with holiday lights at the end of each year for Christmas, a display that grew from about 50,000 lights to 500,000 and takes two months to install. Since 2015 a "Lights of Love" display has lit the garden for Valentine's Day.

The garden and the factory's self-guided tour windows are both free, with no booking needed; the cactus garden opened in September 1981 and sits at 2 Cactus Garden Drive in Henderson. Paths are self-guided, and the site's water-treatment ponds, fed by the factory's dishwater, draw birds. The garden is lit for Christmas from late in the year and for Valentine's Day since 2015.

The garden's ponds are part of a "Living Machine", a wastewater plant added in the mid-1990s that uses bacteria, algae, protozoa, snails and fish to recycle all of the factory's dishwater without chemicals; the treated water irrigates the garden, and the ponds draw the birds that live among the cacti.