Having previously served as an infantry general under Alexander the Great, he eventually assumed the title of basileus and established the Seleucid Empire over much of the territory in the Near East which Alexander had conquered.
Seleucus founded a number of new cities during his reign, including Antioch (300 BC) and in particular Seleucia on the Tigris (ca. 305 BC), the new capital of the Seleucid Empire, a foundation that eventually depopulated Babylon.

Reverse: Zeus seated left, leaning on scepter, holding eagle; ΣEΛEYKOY // (TAYP) // (ΔYP) / BAΣIΛEΩΣ
Die Orientation: -
Weight: 17 g

Reverse: BASILEWS / SELEYKOY, bull butting right, uncertain control monogram between hind legs
Die Orientation: -
Weight: -
Reverse: Anchor, BAΣIΛEΩΣ // ΣEΛEYKOY, monogram
Die Orientation: -
Weight: 4.7 g

Reverse: BAΣIΛEΩΣ ΑΛΕΞΑΝΔΡΟΥ, Zeus Aëtophoros seated left; monogram in wreath in left field, HP monogram below throne.
Die Orientation: 0 H
Weight: 0 g

Reverse: bull butting right; BAΣIΛEΩΣ / ΣEΛEYKOY / Ξ
Die Orientation: -
Weight: 6 g

Reverse: BAΣIΛEΩΣ AΛEΞANΔΡOY - Zeus seated left, holding eagle and sceptre, anchor and YΠA monogram in left field, A beneath chair. BAΣIΛEΩΣ below, AΛEΞANΔPOY to right.
Die Orientation: 11 H
Weight: 16.95 g
Struck in the name of Alexander III.

Reverse: ΒΑΣΙΛΕΩΣ ΑΛΕΞΑΝΔΡΟΥ / MI / MH-Π - Zeus seated left, holding eagle and sceptre. MI over club in left field. MH-Π monogram in wreath below.
Die Orientation: 4 H
Weight: 17.06 g