- O camiño da Estadea
- O centro do labirinto
- O corazón de Xúpiter
- O Gato Michín
- O Menino Longínquo
- O minotauro
- O mistério da luz e a face das sombras
- O paxaro do mel
- O país adormentado
- O que sei do silencio
- Oceans
- Octo-Man and the Headless Monster #1
- Odd One Out
- Odd One Out (Readaloud)
- Odd One Out US Ed (Readaloud)
- Odd! Birds
- Off I Go!: An Acorn Book (Princess Truly #2)
- Off to School
- Off to School (Readaloud)
- Off-Key
- Oh Say Can You Say Di-no-saur? All About Dinosaurs
- Oh Say Can You Seed? All About Flowering Plants
- Oh, Baby! #3
- Oh, the Pets You Can Get!
- Oh, The Things You Can Do That Are Good for You
- Olaf und der gelbe Vogel
- Oliver Twist
- Oliver’s Magic, Book 1: A Family Secret
- Ollie's Odyssey
- Oltre le nuvole
- Oma, ich kann deine Geschichten schon lesen
- On a Cold Day
- On a Hot Day
- On Her Own
- On Ice: Exploring the Arctic with a Polar Bear Cub (#5)
- On Land
- On the Freedom Trail #4
- On the Go
- On the Ice
- On the Job
- On the Job Podcast Producer: Multiplication
- On the Job: Contractors Perimeter and Area
- On the Job: Teachers: Time: Read-along ebook
- On the Road
- On the Road: Ratios and Proportions
- On the Scene: A CSI's Life
- On Thin Ice (Diary of an Ice Princess #3)
- On Water
- On Your Mark, Get Set, Laugh! #13
- Once upon a Mastodon: All About Prehistoric Mammals
- Once Upon the Rhine
- One Big Crafty Family
- One Cent, Two Cents, Old Cent, New Cent
- One Leap Forward
- One Little Piggy: Counting Books for Toddlers
- One Long Day
- One Small Step for Spork (Book 12)
- One Vote, Two Votes, I Vote, You Vote
- Onka Yoruba: My First Naija Numbers
- Only When it Rains
- Open Wide #23
- Operation Twin Trouble
- Opowiesc wigilijna wydanie ilustrowane
- Opposites
- Opposites (Readaloud)
- Opposites With Ria
- Opuestos
- Orgullo y prejuicio
- Origami Magic
- Origin of a Hero (She-Ra Chapter Book #1)
- Original Bedside Stories Book 2
- Orni l'ornitorinco
- Orphelins 88
- Os Zumbis Telefônicos
- Osterhase: Eier Jagt
- Otter Tales
- Osterhase: Eier Jagt
- Otter Tales
- Otter This World
- Otters
- Our Earth
- Our Family Reunion
- Our Favorites
- Our Garden in the City
- Our Harvest Lunch
- Our Leaders in Government
- Our Nation's Capital: Washington, DC
- Our New Car: Ratios and Proportions
- Our Principal Breaks a Spell!
- Our Principal Is a Frog!
- Our Principal Is a Noodlehead!
- Our Principal Is a Scaredy-Cat!
- Our Principal Is a Spider!
- Our Principal Is a Wolf!
- Our Principal's in His Underwear!
- Our Principal's Wacky Wishes!
- Our Resources
- Our School Garden
- Our Solar System
- Our Trip to the City
- Our World Is Relative
- Out in the Snow
- Out in the Snow (Readaloud)
- Out of Remote Control
- Out of Sight Till Tonight! All About Nocturnal Animals
- Out On A Limb
- Out to Lunch #2
- Outer Space
- Outside the Box: Teams
- Over the Bridge of Light
- Overcoming Fear
- Owen and Eleanor Make Things Up
- Owen and Eleanor Meet the New Kid