- Brian Ohl to William Ohlenkamp
- Albert Ohler to Thomas Ohliger
- Cynthia Ohlin to Deborah Ohlson
- Diane Ohlson to Patrick Ohm
- Paul Ohm to Nancy Ohmart
- Robert Ohmart to Robert O'Horo
- Thomas O'Horo to Michael Oien
- Nancy Oien to Matthew Oja
- Melvin Oja to Carmen Ojeda
- Carol Ojeda to Guadalupe Ojeda
- Guillermina Ojeda to Martha Ojeda
- Martin Ojeda to Thomas Ojeda
- Tiffany Ojeda to Moon Ok
- Myung Ok to Susan Okada
- Susumu Okada to George Okamoto
- Glenn Okamoto to Brian O'Kane
- Bridget O'Kane to Elizabeth Oke
- George Oke to Gail O'Keefe
- Garrett O'Keefe to Noreen O'Keefe
- Norma O'Keefe to Timothy O'Keeffe
- William O'Keeffe to Patricia O'Kelley
- Patrick O'Kelley to John Okerlund
- Karen Okerlund to Richard Okita
- James Okkema to Ebele Okonkwo
- Elizabeth Okonkwo to Nneka Okoye
- Obiageli Okoye to Garry Okumura
- Gary Okumura to Carmen Olaez
- Esteban Olaez to Stephanie Olague
- Steven Olague to Fernando Olalde
- Francisco Olalde to Frank Olander
- Gary Olander to Miguel Olarte
- Monica Olarte to Marilyn Olavarria
- Marisol Olavarria to Joseph Olberding
- Julie Olberding to James Olczak
- John Olczak to Stephanie Oldaker
- Stephen Oldaker to Susan Olden
- Sylvia Olden to Terry Oldenburg
- Theresa Oldenburg to Jeanette Oldfield
- Jeff Oldfield to Carolyn Oldham
- Carrie Oldham to Jessie Oldham
- Jewell Oldham to Roger Oldham
- Ron Oldham to Jordan Oldroyd
- Karen Oldroyd to Helen Olds
- Henry Olds to Sara Olds
- Sarah Olds to Joaquin Olea
- Joe Olea to Arlene O'Leary
- Arline O'Leary to Howard O'Leary
- Ian O'Leary to Nicole O'Leary
- Nina O'Leary to Robert Olejar
- Thomas Olejar to Justin Oleksy
- Kathleen Oleksy to John Oleniczak
- Joseph Oleniczak to Margaret Oles
- Maria Oles to Joseph Oleska
- Michael Oleska to Kristi Oleson
- Kyle Oleson to Elizabeth Oley
- Faiz Oley to Daniel Olguin
- Danielle Olguin to Margarito Olguin
- Maria Olguin to Robert Olheiser
- Scott Olheiser to Gloria Olin
- Gordon Olin to Alexander Olinger
- Alfred Olinger to Laura Olinger
- Lauren Olinger to Arthur Oliphant
- Ashley Oliphant to Lynn Oliphant
- Marcus Oliphant to Ana Oliva
- Andrea Oliva to Fernando Oliva
- Fidel Oliva to Luis Oliva
- Luisa Oliva to Sara Oliva
- Sarah Oliva to Amelia Olivares
- Amparo Olivares to Eunice Olivares
- Eusebio Olivares to Luis Olivares
- Luisa Olivares to San Olivares
- Sandra Olivares to Deborah Olivarez
- Debra Olivarez to Marlene Olivarez
- Marta Olivarez to Jose Olivarria
- Juan Olivarria to Donna Olivas
- Dora Olivas to Jose Olivas
- Josefa Olivas to Rachel Olivas
- Rafael Olivas to Bryan Olive
- Carl Olive to Monica Olive
- Myrtle Olive to Benjamin Oliveira
- Bernadette Oliveira to Franklin Oliveira
- Fred Oliveira to Lawren Oliveira
- Lawrence Oliveira to Reva Oliveira
- Rewton Oliveira to Jessica Olivencia
- Jesus Olivencia to Augustus Oliver
- Aurora Oliver to Ceola Oliver
- Cesar Oliver to Demarcus Oliver
- Demetria Oliver to Everett Oliver
- Everlena Oliver to Isaac Oliver
- Isabel Oliver to Karen Oliver
- Kari Oliver to Liam Oliver
- Lianna Oliver to Melinda Oliver
- Melisa Oliver to Prentice Oliver
- Prentiss Oliver to Shantel Oliver
- Shari Oliver to Tressa Oliver
- Trevor Oliver to Catherine Olivera
- Cecilia Olivera to Lilia Olivera
- Lilian Olivera to Alex Oliveras
- Alexander Oliveras to Yolanda Oliveras
- Yvonne Oliveras to Tara Oliveri
- Theresa Oliveri to Jesus Olivero
- Joan Olivero to Manuel Oliveros
- Marco Oliveros to Barbara Olivier
- Barry Olivier to Leslie Olivier
- Leticia Olivier to David Olivieri
- Debbie Olivieri to John Olivito
- Joseph Olivito to Gilbert Olivo
- Gilberto Olivo to Patsy Olivo
- Paul Olivo to Robert Olkiewicz
- Edward Olko to Jonathan Oller
- Jorge Oller to Mae Ollie
- Marcus Ollie to Howard Ollis
- Jack Ollis to Mark Ollom
- Mary Ollom to Ruben Olmeda
- Salvador Olmeda to Nancy Olmedo
- Nicholas Olmedo to Roberto Olmo
- Rosa Olmo to Jamil Olmos
- Jason Olmos to Tony Olmos
- Uriel Olmos to Helen Olmstead
- Henry Olmstead to Shane Olmstead
- Shannon Olmstead to Lynn Olmsted
- Marcia Olmsted to Judy Olney
- Julie Olney to Chris O'Loughlin
- Christine O'Loughlin to Jeanette Olschowka
- Joseph Olschowka to Carla Olsen
- Carlene Olsen to Ebba Olsen
- Ed Olsen to Isabelle Olsen
- Ivan Olsen to Lacey Olsen
- Ladonna Olsen to Miranda Olsen
- Miriam Olsen to Sharron Olsen
- Shaun Olsen to Gary Olshan
- Jeffrey Olshan to Arlene Olson
- Arlie Olson to Carlie Olson
- Carlos Olson to Darrell Olson
- Darren Olson to Erik Olson
- Erika Olson to Howard Olson
- Hubert Olson to Juli Olson
- Julia Olson to Lea Olson
- Leah Olson to Marie Olson
- Marietta Olson to Nina Olson
- Nita Olson to Rosetta Olson
- Rosie Olson to Teresa Olson
- Terese Olson to Annika Olsson
- Arnold Olsson to Jan Olstad
- Jennifer Olstad to Jeremy Olszewski
- Jerome Olszewski to Paul Olszowy
- Peter Olszowy to David Oltmanns
- Donna Oltmanns to Alberta Olvera
- Alberto Olvera to Eloina Olvera
- Eloisa Olvera to Julieta Olvera
- Julio Olvera to Refugio Olvera
- Regina Olvera to Michael Olynick
- George Olynyk to Dale O'Malley
- Dan O'Malley to Madeline O'Malley
- Madison O'Malley to Beverly Oman
- Billy Oman to Zev Oman
- Adrian Omana to Javier Omar
- Jean Omar to Dolores O'Mara
- Donald O'Mara to Dorothy Omary
- Gary Omary to Larry O'Meara
- Laura O'Meara to Sadiya Omer
- Saleh Omer to Miki Omori
- Richard Omori to Terry On
- Thanh On to Veronica Onate
- Victor Onate to Jan Ondra
- John Ondra to Bailey O'Neal
- Barbara O'Neal to Darla O'Neal
- Darlene O'Neal to Glenda O'Neal
- Glenn O'Neal to Kelvin O'Neal
- Ken O'Neal to Mel O'Neal
- Melanie O'Neal to Russel O'Neal
- Russell O'Neal to Whitney O'Neal
- Wilbert O'Neal to Christie O'Neil
- Christina O'Neil to Jackie O'Neil
- Jaclyn O'Neil to Mark O'Neil
- Marlene O'Neil to Tanya O'Neil
- Tara O'Neil to Cameron O'Neill
- Camille O'Neill to Fern O'Neill
- Fernando O'Neill to Kendra O'Neill
- Kenneth O'Neill to Norman O'Neill
- Olga O'Neill to Vernon O'Neill
- Veronica O'Neill to Gerald Oney
- Glen Oney to Beng Ong
- Benjamin Ong to Jeffery Ong
- Jeffrey Ong to Rachel Ong
- Ramon Ong to Donald Onge
- Donna Onge to Sandra Onisko
- Daniel Onita to Debra Ono
- Diane Ono to Eduardo Onofre
- Elizabeth Onofre to Andrew Onorato
- Angela Onorato to Frank Onstott
- George Onstott to Cinthia Ontiveros
- Cinthya Ontiveros to Jorge Ontiveros
- Jose Ontiveros to Rosalinda Ontiveros
- Rosalio Ontiveros to George Onyango
- John Onyango to Laura Ooms
- Maria Ooms to David Opalka
- Edward Opalka to Thomas Opdyke
- Timothy Opdyke to Wayne Opfer
- William Opfer to Daniel Opitz
- David Opitz to Kwasi Opoku
- Lewis Opoku to Rocco Oppedisano
- Rose Oppedisano to Linda Oppenheim
- Lisa Oppenheim to Sandra Oppenheimer
- Sarah Oppenheimer to Patrick Opperman
- Paul Opperman to George Oprean
- Kathleen Oprean to Christina Oquendo
- Christine Oquendo to Natasha Oquendo
- Neftali Oquendo to Clyde Oquinn
- Cody Oquinn to Ronald Oquinn
- Ronnie Oquinn to Joan Oram
- Joann Oram to Betty Orange
- Beverly Orange to Rodney Orange
- Roger Orange to John Orapallo
- Frank Orapello to Jeffrey Orban
- Jennifer Orban to Chris Orchard