The Apple Watch Series 9 (45mm, GPS, Starlight) is Apple's 2023 flagship smartwatch featuring the new S9 SiP chip with a 64-bit dual-core processor and 4-core Neural Engine, delivering significantly faster performance and the new Double Tap gesture for hands-free control. The 45mm Starlight aluminum case pairs with a Starlight Sport Band in S/M sizing (fits wrists 140–245mm), and the Always-On Retina LTPO OLED display reaches up to 2000 nits brightness with 326 pixels per inch behind Ion-X front glass.

Health and safety features include ECG, blood oxygen monitoring, third-generation optical heart sensor, temperature sensing, sleep stage tracking, cycle tracking with retrospective ovulation estimates, high and low heart rate notifications, and irregular rhythm notifications. The watch includes Fall Detection, Crash Detection, and Emergency SOS with international emergency calling. It is water resistant to 50 meters (ISO 22810:2010) and carries an IP6X dust resistance rating.

Fitness tracking covers an extensive range of workouts including running with stride metrics and automatic track detection, cycling with power zone and Bluetooth accessory support, swimming with automatic stroke detection, hiking with topographic maps for over 1,000 U.S. national and regional parks, and more than 20 additional workout types. GPS is built-in (L1, GNSS, Galileo, BeiDou), with Wi-Fi 4 (802.11n), Bluetooth 5.3, a second-generation Ultra Wideband chip, and Apple Pay support. Battery life is rated up to 18 hours with normal use and up to 36 hours in Low Power Mode, with fast-charge capability delivering up to 80% charge in approximately 45 minutes. The case is made from 100% recycled aluminum and is part of Apple's first carbon-neutral product lineup under the Apple 2030 initiative.