AN OBJECT OF THE INVENTION IS TO DEVELOP FIBERS WHICH INCLUDE AN OLEFIN POLYMER AND ARE SUITABLE TO FORM A NONWOVEN FABRIC, AND TO DEVELOP SUCH NONWOVEN FABRICS. THE INVENTION PROVIDES A FIBER INCLUDING AN OLEFIN POLYMER COMPOSITION INCLUDING 100 PARTS BY WEIGHT OF AN OLEFIN POLYMER AND 0.1 TO 30 PARTS BY WEIGHT OF AN ACID-FORM ANIONIC SURFACTANT, THE ACID-FORM ANIONIC SURFACTANT HAVING BEEN MELT KNEADED IN THE FIBER.