Omega-9 fatty acids, primarily oleic acid, are monounsaturated fats. Your body produces them, so you do not require them from food. Foods like olive oil, avocados, and nuts provide oleic acid. Swapping saturated fats for monounsaturated fats supports heart health, but taking an omega-9 supplement has not been shown to offer benefits beyond a good diet.
You rarely find omega-9 sold alone as a supplement. It appears in combination omega oils or as a carrier oil in softgels. No strong evidence shows it helps with joint health, blood sugar management, or other targeted effects.