Catriona Gray

On September 5, 2016, Gray was announced one of the 40 candidates competing for the title of Miss World Philippines 2016. The pageant was held on October 2, at the Manila Hotel. Early in the competition, Gray won four special awards—Best in Swimsuit, Best in Evening Gown, Best in Fashion Runway, and Best in Talent—as well as six awards from the pageant's corporate sponsors.

Gray would progress to the Top 12 question and answer round she was asked, "When you get up in the morning and look in the mirror, what do you see?". In her answer she recalled how she would reflect on her experiences to further her character.

"I see someone who is constantly trying to be better. I've always endured to always be better than the day before, to do things that challenge me, to do things outside the box. And something that is very fulfilling that I have found is when I look in the mirror, I want to see someone who gives back to the community, and that's someone who I achieve to be every single day."

During the final question and answer round all the five finalists were asked the same question, "Why should you be Miss World Philippines 2016?". Gray emphasized her commitment to her title and her personal advocacy in her answer.

"To be a Miss World is to be passed a torch that burns with passion and purpose. If I am to become Miss World Philippines, I will dedicate my voice and essence to carry that torch and to set charitable causes alight, such as my personal advocacy, the Paraiso Bright Beginnings Project. And I would focus on passing on this torch to empower others because I believe together there is no darkness in this world that our light cannot overcome."

On September 3, 2017, Gray crowned Laura Lehmann as her successor at the Miss World Philippines 2017 pageant.

After winning the national competition, Gray competed at Miss World 2016 held in MGM National Harbor, in Oxon Hill, Maryland, United States. In pre-pageant contests, Gray won the Multimedia Award, placed second for the Talent Award, and placed in the top five for the Beauty with a Purpose project.

During the question and answer portion in the pageant, she was asked by the reigning Miss World 2015 Mireia Lalaguna, "Which qualities do you think it will take to wear my crown?". She would state "bravery" as the quality necessary for the title.

"I think, first of all, it takes bravery. To be a Miss World is to carry a burning torch. It is like action carried out by one to illuminate the lives of many. And I would dedicate my whole self, my love for the arts and my voice to try to uplift, empower and educate people. And it would be my greatest honor and duty to hold this torch high enough so that all the world could feel and see its light. Thank you."

Gray went on to finish as a Top 5 finalist. Stephanie Del Valle of Puerto Rico won the said pageant.

On January 8, 2018, Gray submitted her application for the Binibining Pilipinas 2018 pageant. On January 16, she was confirmed as one of the 40 candidates competing for the six national titles contested in the pageant.

During the national costume competition on March 3, Gray wore a Mindanao-inspired golden princess gown designed by Jearson Demavivas in honor of Muslim women affected by the Siege of Marawi the previous year. She was announced as one of the ten finalists for the Best in National Costume Award on March 9.

The pageant was held on March 18, at the Araneta Coliseum. Gray won five special awards: Best in National Costume. Best in Evening Gown, and two awards from the pageant's sponsors. She also obtained two popularity contest prizes.

Gray would progress to the question and answer round, where United States Ambassador to the Philippines Sung Yong Kim asked the following: "After the devastating war—Marawi is now on its way to recovery, what will be your message to the young women of Marawi?". Gray would state the following:

"My answer and my message to the women is to be strong. As women, we're the head of the household and we have amazing influence, not only in our own families, as mothers, sisters and friends, but also in our community. If we could get the women to stay strong and be that image of strength for the children and the people around them, then once the rebuilding is complete and is underway, the morale of the community will stay strong and high."

Gray would go on to win the pageant as Miss Universe Philippines 2018, being crowned by her predecessor Rachel Peters. With her victory, Gray became the first Filipino to represent the country in both the Miss World and Miss Universe competitions, and the second to represent the Philippines in two major international pageants, the first being Carlene Aguilar in 2005.

On June 9, 2019, Gray crowned Gazini Ganados as her successor at the Binibining Pilipinas 2019 pageant.

As Miss Universe Philippines 2018, Gray represented the Philippines at the Miss Universe 2018 pageant.

During the national costume show presentation on December 10, Gray showcased a beaded tribal suit featuring the indigenous tribes of the ancient pagan Filipinos, alongside an oversized Parol painted lantern pulled by a roller device. The costume was accompanied by a pre-Christian Shamanic dance of the historical Babaylan paganism. The costume gained both praise and criticism, due to the perceived difficulty of walking and the failure of LEDs to function. Gray cited her scoliosis for such issues.

In the pageant's preliminary contest, Gray did a slow-motion walk, billed as the "lava walk", on the ramp in the swimwear competition wearing a pink swimsuit, which was praised by supermodels Tyra Banks and Ashley Graham, fashion commentators and Internet viewers. At the preliminary evening gown competition, she wore Mak Tumang's golden sweetheart gown with a thigh-high slit inspired by the Ibong Adarna and the Mikimoto crown.

The pageant was held on December 17 at the Impact Arena, Muang Thong Thani, in Thailand. At the beginning of the competition, Gray advanced to Top 20. During the opening statement segment, Gray recalled her experiences in working with a non-profit organization.

"Working in some of the poorest areas of my country, I found that it was a lack of child support, not poverty, that killed their dreams. A child once told me, 'Cat, that's just not my life, and those dreams aren't made for me.' But I stand here today because someone believed in me and we owe it to our children to believe in them."

Gray advanced to Top 10. She wore a pink Sirivannavari bikini and a cape with gold-winged shoulder straps at the swimsuit competition. At the evening gown competition, she wore a Mak Tumang design made of tulle encrusted with Swarovski crystals in 12-toned color palette that ranged from yellow to dark red dubbed the Mayon gown. Its body-fitting, bare back design features a side cutout and a high slit that "highlighted Gray's legs". The dress, which according to Tumang weighed 10 pounds, was a tribute to Mayon Volcano, a tourist attraction in the province of Albay, the hometown of Gray's mother. In an interview, Gray decided to pick the gown for the beauty pageant as her mother dreamed of her winning the Miss Universe crown wearing a red dress.

Gray then advanced to Top 5. During the first question and answer round, Gray was asked by host Steve Harvey, "Canada recently joined Uruguay as the second nation in the world to make marijuana legal. What is your opinion on the legalization of marijuana?" She responded:

"I'm for it being used for medical use, but not so for recreational use. Because I think if people were to argue: Then what about alcohol and cigarettes? Well, everything is good but in moderation."

Gray advanced to Top 3. In the final question and answer portion, the top three contestants were asked the same question by Harvey: "What is the most important lesson you've learned in your life and how will you apply it to your time as Miss Universe?" She answered:

"I work a lot in the slums of Tondo, Manila, and the life there is very... it's poor and it's very sad. And I've always taught myself to look for the beauty in it; to look in the beauty in the faces of the children, and to be grateful. And I would bring this aspect as a Miss Universe to see situations with a silver lining, and to assess where I could give something, where I could provide something as a spokesperson. And this I think if I could also teach people to be grateful, we could have an amazing world where negativity could not grow and foster, and children will have a smile on their faces."

At the end of the event, Gray won the competition and was crowned by her predecessor, Demi-Leigh Nel-Peters of South Africa. She is the fourth Filipino Miss Universe after Gloria Diaz in 1969, Margie Moran in 1973, and Pia Wurtzbach in 2015. In addition, she is the second Biracial Filipina to win the Miss Universe title after Wurtzbach.

On December 20, 2018, Gray made a courtesy call with President Rodrigo Duterte at the Villamor Airbase in Pasay.

On January 22, 2019, Gray traveled to Indonesia to shoot a commercial for C 1000, a vitamin brand in Indonesia.

On February 16, 2019, Gray arrived in the Philippines for a week-long homecoming celebration with visits to the cities of Manila, Makati, Pasay and Quezon City. However, on February 23, 2019, The feather of the Mikimoto Crown fell off during her homecoming parade in Araneta Center, Cubao, Quezon City. She also made courtesy calls to the Congress of the Philippines, Senate of the Philippines and Malacañang Palace.

On October 17, 2019, Gray attended the 2019 Latin Music Awards at the Dolby Theatre, Hollywood and Highlands in Los Angeles, California, where she presented the 2019 "Canción Favorita – Tropical" award for the song "Adicto" to Marc Anthony and Prince Royce.

On December 5, 2019, Gray attended the release of the new Mouawad Crown for the Miss Universe pageant, which is nicknamed Power of Unity, thus retiring the Mikimoto Crown.

In her capacity as Miss Universe, Gray visited Brazil, Indonesia, Thailand, South Africa, various cities and states across the United States, and her home country of the Philippines. She also visited Canada and United Arab Emirates to meet with her pageant sponsors and Filipino supporters.

On December 8, 2019, Gray crowned Zozibini Tunzi of South Africa as her successor at the 68th Miss Universe pageant.

Gray has advocated for women's rights, indigenous culture conservation, and the "One Town, One Product" (OTOP) project of the Philippines' Department of Trade and Industry. She has continued to pursue her women's rights advocacies despite some incidents when military officials attempted to pressure her into limiting her interactions with certain women's rights groups. Gray has been working with the organization Young Focus Philippines since May 2016. She is also a Love Yourself Philippines and Smile Train ambassador. During the COVID-19 pandemic, Gray served as an ambassador of the Philippine Red Cross.

In February 2020, the Philippines' National Commission for Culture and the Arts (NCCA) designated Catriona Gray as the agency's Ambassador for the Arts. Gray was named ambassador yet again in 2021, and was announced as host for "Kultura 101", an NCCA Web Series where Gray said she would "share [her] passion for aspects of Filipino culture whether it be our textiles, our dances, our food."

Gray was also named an Ambassador for Indigenous Handicrafts by the Philippines' Department of Trade and Industry in July 2020.

Gray responded strongly when she was drawn into the Philippines' Red-tagging issue, due to an incident in October 2020 when AFP Southern Luzon Command commande Antonio Parlade Jr. said that Gray and actress Liza Soberano should not support Gabriela and other rights groups, as fellow celebrity Angel Locsin has done, or they would be drawn into the activities of the Marxist-Leninist-Maoist New People's Army, and risk being killed in a clash with the army just like activists who had allegedly joined that group.

In response, Gray's lawyer Joji Alonso issued a statement saying Parlade's statements were "uncalled for" and affirmed that Gray would continue to advocate for social causes concerning women and will remain "steadfast in her stance that no one should be silenced in sharing their personal stories".