The Republican-dominated Kentucky legislature voted overwhelmingly on Wednesday to override the governor’s veto of a bill that will create a host of new regulations and restrictions on transgender youth, including banning access to what doctors call gender-affirming health care.

The bill, described by L.G.B.T.Q. rights groups as among the most extreme in the nation, was vetoed on Friday by Gov. Andy Beshear, a Democrat, but it was overridden in both the State House and Senate, where Republicans hold supermajorities.

The law, which began as a fairly narrow bill but steadily grew into a much larger package of restrictions, specifically bans surgeries, puberty blockers and hormone therapy for children under 18. It also forbids school districts from requiring or recommending that students be referred to by pronouns that “do not conform to a student’s biological sex as indicated on the student’s original, unedited birth certificate.”

The law also compels doctors to cease treating patients who are undergoing gender-transition care, adding that if physicians deem that ceasing treatment is likely to “harm the minor,” they may set a time frame to “systematically” phase out treatment.

In addition to the new rules governing transgender youth, the law also puts limits on what can be discussed in schools, requiring schools to give notice to parents about any program on the subject of sexuality, barring teaching on sexuality below the sixth-grade level and banning lessons at any grade level about gender identity or sexual orientation.

The law is part of a wave of legislation filed in recent years by Republican state lawmakers to restrict and regulate the lives of transgender youth. At least 10 states have passed similar bans on transition care, including Arizona, Florida, Georgia, Iowa, Tennessee and Utah.

On Wednesday, the governor of West Virginia signed a bill into law that will also ban transition care for minors unless the child has been “diagnosed as suffering from severe gender dysphoria” by at least two health care providers and has parental consent. In two more states — Idaho and Missouri — the passage of bans appears imminent, according to Erin Reed, a legislative analyst who is opposed to bills limiting access to transgender medical care.

“We are going to have to survey the damage” after this legislative session concludes, Ms. Reed said. “But I do think that most of these bills are going to be overturned in court, and I’m hopeful that the next wave of news in the summer brings some level of relief to trans Americans.”

Arkansas was the first state to pass a ban on medical care for transgender minors, which sparked a court fight that has prevented the ban from taking effect. The Kentucky chapter of the American Civil Liberties Union has vowed to challenge the state’s law in the courts, meaning that its implementation, too, will most likely be delayed.

While the Kentucky override happened quickly, it was largely expected given the state legislature’s strong conservative bent. The vote fell almost, though not entirely, along party lines.

Mr. Beshear, a first-term governor, came to office by defeating a particularly unpopular Republican incumbent, Matt Bevin, who had picked fights with teachers throughout his term. Mr. Beshear is up for re-election this year, and his holding onto the office is hardly a given in a state that former President Donald J. Trump won in 2020 by 26 percentage points. Still, Mr. Beshear has maintained a sturdy popularity by focusing on practical governance, including responding to an exhausting barrage of natural disasters that has pummeled Kentucky over the last four years.

But the intense emotions around the issues of schools, gender and sexual identity are much more politically volatile. An attempt this month by a group of Republican state senators to soften a version of the bill, removing some of its more controversial elements, fizzled after a conservative Christian group organized a letter-writing campaign. Then on Wednesday, people opposed to the bill came by the hundreds to the State Capitol to protest.

With the shouts and chants of demonstrators ringing out behind him, State Senator Max Wise, a Republican and the bill’s sponsor, declared that the goal of his legislation “was to strengthen parental engagement and communication in children’s education while protecting the safety of our children.”

Mr. Wise took particular issue with Mr. Beshear’s remarks in a statement accompanying his veto that the bill would turn teachers into investigators.

In that statement, Mr. Beshear also said that the bill “strips freedom from parents to make personal family decisions” and warned that it would “cause an increase in suicide among Kentucky’s youth.”

Henry Berg-Brousseau, a 24-year-old transgender activist who appeared at legislative hearings to lobby against such bills, died by suicide in December. His mother, Dr. Karen Berg, is a Democratic state senator, and spoke out against the bill on Wednesday.

“To say this is a bill protecting children is completely disingenuous,” she said on the floor of the Senate. “And to call this a parents’ rights bill is an absolute despicable affront to me personally.”