A lei was a traditional flowered garland from the Polynesian cultures of Earth. The garland was seen as a representation of the flowering of love and was worn around the neck.
During a party aboard USS Discovery on stardate 2136.8, Ash Tyler and several other crew members wore leis made of white imitation flowers. (DIS: "Magic to Make the Sanest Man Go Mad")
In 2373, Neelix created a Polynesian-type resort hologram program in which the crew of USS Voyager wore leis during a luau. Tuvok was the only person present who chose to refrain from wearing one, something which was pointed out by Marayna, who stated that she believed he was trying to isolate himself and stage a public protest at the same time. Later, when Marayna took control of the Voyager systems, a holoprogram character attempted to strangle Lieutenant B'Elanna Torres using a lei. (VOY: "Alter Ego")