In Ancient Greece a thyrsus (/ˈθɜːrsəs/) or thyrsos (/ˈθɜːrsɒs/; Ancient Greek: θύρσος) was a wand or staff of giant fennel (Ferula communis) covered with ivy vines and leaves, sometimes wound with taeniae and topped with a pine cone, artichoke, fennel, or by a bunch of vine-leaves and grapes or ivy-leaves and berries, carried during Hellenic festivals and religious ceremonies. The thyrsus is typically associated with the Greek god Dionysus (and his subsequent Roman equivalent Bacchus) as a symbol of prosperity, fertility, and hedonism.

In Greek religion, the staff was carried by the devotees of Dionysus. Euripides wrote that honey dripped from the thyrsos staves that the Bacchic maenads carried. The thyrsus was a sacred instrument at religious rituals and fêtes.

The fabulous history of Bacchus relates that he converted the thyrsi carried by himself and his followers into dangerous weapons, by concealing an iron point in the head of leaves. Hence his thyrsus is called "a spear enveloped in vine-leaves", and its point was thought to incite to madness.

The thyrsus, associated with the followers of Dionysus (the satyrs, thiasus, and maenads or Bacchantes), is a symbol of prosperity, fertility, hedonism, and pleasure/enjoyment in general. The thyrsus was tossed in the Bacchic dance:

Pentheus: The thyrsus—in my right hand shall I hold it?

Dionysus: In thy right hand, and with thy right foot raise it.

In the Iliad, Diomedes, one of the leading warriors of the Achaeans, mentions the thyrsus while speaking to Glaucus, one of the Lycian commanders in the Trojan army, about Lycurgus, the king of Scyros:

He it was that/drove the nursing women who were in charge/of frenzied Bacchus through the land of Nysa,/and they flung their thyrsi on the ground as/murderous Lycurgus beat them with his oxgoad.