S
- Shredded Oats – Barbara's Bakery, 1980s
- Shreddd Spoonfuls – Barbara's Bakery, 1980s
- Shredded Wheat – Post Cereals (originally Nabisco Shredded Wheat) Barbara's Bakery (US), Cereal Partners (UK) – (variants and generic versions sold under various names)
- Shreddies – General Mills/Cereal Partners (generic equivalent sold under many different names)
- Shrek's (NOT Donkey's) – Shrek-themed cereal made by General Mills
- Sir Grapefellow – General Mills (1972)
- Slimer! And The Real Ghosterbusters Cereal – Ralston ( Early 1990s)
- Honey Smacks – Kellogg's (originally "Sugar Smacks")
- Smart Bran
- Smart Start
- S'mores Grahams or S'mores Crunch – General Mills (1980s–1990s)
- Smorz – Kellogg's (2003 – present)
- Smurf Berry Crunch – Post Cereals (1983)
- Smurf Magic Berries – Post Cereals (1987-Early 1990s)
- Snow Flakes – Nestlé (Eastern Europe, Asia and South America)
- Special K – Kellogg's (1955 – present)
- Special K Chocolatey Delight – Kellogg's
- Special K Cinnamon Pecan – Kellogg's
- Special K Blueberry – Kellogg's
- Special K Red Berries – Kellogg's (2001 – present)
- Special K Vanilla Almond – Kellogg's
- Special K Fruit and Yogurt – Kellogg's
- Special K Protein Plus – Kellogg's
- Spider-Man – Ralston (1995)
- Spider-Man Cereal – Kellogg's (2002) (2004)
- Spiderman 3 Cereal – General Mills (2007)
- SpongeBob SquarePants – Kellogg's (2004–2007)
- Sprinkle Spangles – General Mills (Early 1990s)
- Stars – Kellogg's (1960s)
- Star Wars cereal – Kellogg's (c.2005)
- Start – Kellogg's
- Strawberry Blasted Honeycomb – Post Cereals
- Strawberry Squares – Kellogg's (1980s)
- Strawberry Shortcake – General Mills (1980s)
- Sugar Crisp – Post Cereals (1949 – present)
- Sugar Jets – General Mills (1950s)
- Sugar Puffs
- Sugar Sprinkled Twinkles – General Mills (1960–1965)
- Sultana Bran – Kellogg's (Australia and New Zealand)
- Sun Crunchers – General Mills (discontinued) (1990s)
- Sun Flakes – Ralston (discontinued)
- Superman Stars – Post Cereals
- Sweetened Wheat-fuls – Mom's Best Naturals
- S.W. Graham – Kellogg's (1980s)
Read more about this topic: List Of Breakfast Cereals