Year 1999 (MCMXCIX) was a common year of the Gregorian calendar that started on a Friday. It is the first year of SpongeBob, and the year of episodes with the most in the Hillenburg era.
29 episodes premiered this year.
- May 1 - Help Wanted, Reef Blower, and Tea at the Treedome, the pilot episodes, premiered, thus starting the series.
- July 17 - Bubblestand and Ripped Pants premiered, officially starting the series.
- July 31 - Jellyfishing and Plankton! premiered.
- August 7 - Naughty Nautical Neighbors and Boating School premiered.
- August 14 - Pizza Delivery and Home Sweet Pineapple premiered.
- August 21 - MermaidMan and BarnacleBoy and Pickles premiered.
- August 28 - Hall Monitor and Jellyfish Jam premiered.
- September 4 - Sandy's Rocket and Squeaky Boots premiered.
- September 11- Opposite Day and Nature Pants premiered.
- September 18 - Culture Shock and FUN premiered.
- September 25 - MuscleBob BuffPants and Squidward the Unfriendly Ghost premiered.
- October 2 - The Chaperone and Employee of the Month premiered.
- October 28 - Scaredy Pants and I Was a Teenage Gary premiered. After that, the next new episodes didn't air until December 31 because of a 63-day hiatus.
- December 31 - SB-129 and Karate Choppers (last episodes to air this year) premiered.