- ONE TOUCH OF MOONDUST
- One Touch of Moondust & A Man You Can Trust
- ONE TOUGH TEXAN
- ONE TRUE LOVE?
- One True Loves
- One True Secret
- One Way Ticket to Paris
- One Week Girlfriend: One Week Girlfriend Book 1
- One Week in Mazatlan
- One Week with her (Ex) Stepbrother
- One Week with her Husband
- One Week with her Rival
- One Whopper of a Love Story: A Sweet Romantic Comedy
- ONE WICKED NIGHT
- One Wicked Week
- ONE WILD WEEKEND
- One Winter Morning
- One Winter's Day
- One Winter's Night
- One Winter's Sunset
- One Wrong Step
- One-Click Buy: August 2009 Silhouette Desire
- One-Click Buy: July 2009 Harlequin Presents
- One-Click Buy: October Harlequin Presents
- One-Click Buy: September 2009 Harlequin Presents
- One-Click Buy: September Silhouette Desire
- One-Night Alibi
- One-Night Baby
- One-Night Love Child
- One-Night Man
- One-Night Stand-In
- Online Dating
- ONLY A MEMORY AWAY
- ONLY A WHISPER
- Only An Alaskan Will Do
- ONLY BACHELORS NEED APPLY
- Only Ever After
- Only for You
- Only Him
- Only October
- ONLY ONE GROOM ALLOWED
- Only One Lauren: All The Wrong Reasons Season Premiere
- Only Skin Deep
- Only the Heart Remembers
- Only This
- Only Tim Sent Flowers ~ Revised Edition
- Only You
- ONLY YOU
- Only You
- Only You I Love
- Ontmoeting in het kunstcafé
- Ooh Baby, Baby
- Ooh Baby, Baby Part 1
- Ooh Baby, Baby Part 2
- Ooh Baby, Baby Part 3
- Ooh La La
- Oops!
- Oops, I Hexed It Again: Magic and Mayhem Universe
- OOPS...WE'RE MARRIED?
- Oopsie Daisy: A Steamy Romantic Comedy
- Open Fields
- Open House
- Open your eyes, Dude
- Operation Baby Rescue
- Operation Bailey Babies
- Operation Bailey Birthday
- Operation Bailey Wedding
- Operation Billionaire Trilogy: A Romantic Comedy Boxed Set
- Operation Blind Date
- Operation Gigolo
- Operation Love
- OPERATION MOMMY
- Operation Paradise
- Operation Sizzle
- Operation Unleashed
- Operation: Christmas Seduction
- Operation: Get her back
- Operation: Married by Christmas
- Opportunity Knox
- Opposite of Frozen
- Opposites Distract
- Opposites Ignite
- Ora e per sempre (La locanda di Sunset Harbor—Libro 1)
- Orcas
- Order of the Blade Boxed Set (Books 1-4)
- Ordinary Girl in a Tiara
- Ordo Draconum: The Lazarus Vial
- Orgullo y prejuicio
- Original Cyn
- Os delírios de Natal de Becky Bloom
- Ostrich and the 'Roo
- Other People's Business
- Otherwise Engaged
- OTHERWISE ENGAGED
- Ottercombe Bay – Part Four
- Ottercombe Bay – Part One
- Ottercombe Bay – Part Three
- Ottercombe Bay – Part Two
- Our First Dance
- Our First Embrace
- Our First Kiss
- Our Lady of the Roses
- Our Secret: A College Bully Romance
- Our Star-Crossed Kiss
- Our Urban Utopia
- Out for the Count
- Out in the Blue
- Out of a Dream
- Out of Body
- Out of Character
- Out of Control
- OUT OF CONTROL
- Out of Control
- Out Of Line
- Out of Nowhere
- Out of Olympus Box Set (Books 1 - 4)
- Out of Order
- Out of the Blue
- OUT OF THE BLUE
- Out of the Frying Pan
- Out of the Night
- Out of the Office
- Out of the Shadows
- Out of this World
- Out of Uniform
- Out on a Limb
- Out to Lunch
- Out With A Bang
- Out with the Ex, In with the New
- Out with the Old, In with the New
- Out!
- Out-lanta
- Outback Angel
- Outback Baby
- OUTBACK BABY
- Outback Baby Miracle
- Outback Bachelor
- Outback Boss, City Bride
- Outback Bridegroom
- Outback Fire
- Outback Heiress, Surprise Proposal