Nikolas Jacob Cruz (born September 24, 1998) is an American mass murderer who perpetrated the Parkland high school shooting, where he fatally shot fourteen students and three staff members, and injured seventeen others, on February 14, 2018. In November 2022, Cruz was sentenced to life imprisonment without the possibility of parole for the shooting, which remains one of the deadliest school shootings in the United States.

Cruz had been known for behavioral problems since preschool, and as a teenager on social media he shared his obsessions with mass shootings and expressed racist, sexist, antisemitic, xenophobic, and homophobic views. He was a member of the Junior Reserve Officers' Training Corps. He legally purchased various firearms before the shooting.

Cruz was born to Brenda Norma Woodard (June 25, 1956 – August 23, 2021) on September 24, 1998, in Margate, Florida. His biological father's identity is unknown. Nikolas was placed in an orphanage after his birth and was adopted by Roger and Lynda Cruz. Both adoptive parents died before Cruz finished high school: Roger died at age 67 on August 11, 2004; and Lynda at age 68 on November 1, 2017. Cruz was fully orphaned three months before the shooting. Since his adoptive mother's death, he had been living with relatives and friends.

Cruz was a member of the Junior Reserve Officers' Training Corps and had received multiple awards including academic achievement for "maintaining an A grade in JROTC and Bs in other subjects", according to CNN. He was also a member of his school's varsity air rifle team. At the time of the shooting, he was enrolled in a GED program and employed at a local Dollar Tree.

Cruz had behavioral issues since preschool, and was eligible for special education services alongside an IEP. According to The Washington Post, he was "well known to school and mental health authorities and was entrenched in the process for getting students help rather than referring them to law enforcement". Psychiatrist Dr. Stephen E. Moskowitz diagnosed Cruz with attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD). Cruz was transferred between schools (including Marjory Stoneman Douglas High School) six times in three years in an effort to deal with these problems. In 2014, he was transferred to a school for children with emotional or learning disabilities. There were reports that he made threats against other students.

Cruz returned to Stoneman Douglas High School two years later but was expelled in 2017 for disciplinary reasons. As he could not be expelled from the Broward County school system completely, he was transferred to alternative placement. The school administration had circulated an email to teachers, warning that Cruz had made threats against other students. The school banned him from wearing a backpack on campus.

Psychiatrists recommended an involuntary admission of Cruz to a residential treatment facility, starting in 2013. The Florida Department of Children and Families investigated him in September 2016 for Snapchat posts in which he cut both his arms and said he planned to buy a gun. At this time, a school resource officer suggested he undergo an involuntary psychiatric examination under the provisions of the Baker Act. Two guidance counselors agreed, but a mental institution did not. State investigators reported he had depression, autism, and attention deficit hyperactivity disorder (ADHD), and had a history of attempting suicide. However, psychologist Frederick M. Kravitz later testified that Cruz was never diagnosed with autism. In their assessment, the investigators concluded he was "at low risk of harming himself or others". He had previously received mental health treatment, but had not received treatment in the year leading up to the shooting.

The school district conducted an assessment of the handling of Cruz. According to their redacted report, which was reviewed in August 2018 by The New York Times, The Daily Beast, and other media, a year before the shooting, Cruz had sought help from education specialists, as his grades at Stoneman Douglas were declining. He was an eighteen-year-old junior, and met with the specialists with his mother. The specialists recommended that he transfer to another school, Cross Creek School in Pompano Beach, where he had done well before, but he wanted to graduate with his class at Stoneman Douglas, and rejected this option, as a legal adult. He was advised that if he stayed, he would no longer be able to access special education services, but this was incorrect. A few months later, he withdrew because of failing grades. After that, Cruz requested to go to Cross Creek, but he was told a new assessment was needed, delaying action, and the request was denied.