After watching “Navalny,” the documentary about the Russian opposition leader Aleksei A. Navalny, a Chinese businesswoman messaged me, “Ren Zhiqiang is China’s Navalny.” She was talking about the retired real estate tycoon who was sentenced to 18 years in prison for criticizing China’s leader, Xi Jinping.

After Mr. Navalny’s tragic death this month, a young dissident living in Berlin posted on X, “Teacher Li is closest to the Chinese version of Navalny.” He was referring to the rebel influencer known as Teacher Li, who used social media to share information about protests in China and who now fears for his life.

There are others: Liu Xiaobo, a Nobel Peace Prize laureate who died in government custody in 2017, and Xu Zhiyong, the legal scholar who is serving 14 years in prison on charges of subversion.

The sad fact is that there’s no Chinese equivalent of Mr. Navalny because there’s no opposition party in China, and therefore no opposition leader.

It’s not for lack of trying. Many courageous Chinese stood up to the most powerful authoritarian government in the world. Since 2000, the nonprofit humanitarian organization Duihua has recorded the cases of 48,699 political prisoners in China, with 7,371 now in custody. None of them has the type of name recognition among the Chinese public that Mr. Navalny did in Russia.

Under President Vladimir V. Putin, Russia is highly intolerant of dissent. Mr. Putin jails his critics and hunts them down even in exile. In China, Navalny counterparts as high-profile figures could not exist. They would be silenced and jailed long before they could reach the public awareness.

“Can you imagine the PRC giving noted political prisoners the continuing access that Navalny had to public opinion via various direct and indirect methods?” Jerome Cohen, a retired law professor at New York University, wrote on X, referring to China’s full name, the People’s Republic of China.

That was what members of the Chinese dissident community were thinking as they watched the news of Mr. Navalny’s death with grief and horror. His death was tragic and his life heroic. But it was hard for them to process the revelations that he was able to send hundreds of handwritten letters from jail. People wrote to him, paying 40 cents a page, and received scans of his responses. A video link of him behind bars during his last court appearance was released online.

“Despite increasingly harsh conditions, including repeated stints in solitary confinement,” my colleague Anton Troianovski wrote, “he maintained a presence on social media, while members of his team continued to publish investigations into Russia’s corrupt elite from exile.”

None of that would be possible in China. The names of most Chinese political prisoners are censored online. Once arrested, they are never heard from again. No one can visit them except their direct relatives and their lawyers, although that is not guaranteed. China’s political prisoners cannot correspond with the outside world and are left to rot behind bars, even if they are struggling with health problems — exactly how Mr. Liu, the Nobel Peace Prize laureate, died from late-stage liver cancer in government custody.

Some people call Mr. Ren, the retired real estate tycoon, “China’s Navalny.” He once had probably the highest public profile among Chinese political prisoners. He was among the country’s most influential social media bloggers, with nearly 38 million followers. In 2016, his Weibo account was deleted after he criticized Mr. Xi’s declaration that all Chinese news media had to serve the party.

Last year, when I mentioned him to a young Chinese, the man gave me a blank look. He was 15 when Mr. Ren was silenced and had no idea who he was.

I’ve known Mr. Ren since 2010. But since his arrest in March 2020, I have had no direct communication with him. Nor have his friends. None of us has firsthand knowledge of his life in prison.

Days before his arrest, Mr. Ren told me that he was scheduled for a biopsy on suspicion of prostate cancer. For months, I have heard from people who communicated with his family that he is not getting proper treatment for his prostate conditions and that he is getting up a dozen times a night to go to the toilet. I cannot reach out to members of his family because giving interviews to foreign media can get them in trouble.

Gao Zhisheng was a human rights lawyer who spent years in jail and was tortured, and then disappeared in 2017. His family has not heard from him since. No one knows his whereabouts or even whether he is alive. By now, very few Chinese know his name.

“Their disappearance is a common occurrence,” wrote Guo Yushan, an activist who helped the lawyer Chen Guangcheng seek asylum in the United States in 2012. “They are driven to extinction by the system, shunned and guarded against by mainstream society, forgotten by the public,” Mr. Guo said. “And often, the more thorough their resistance, the more thorough their disappearance.”

Mr. Guo wrote those words in 2013, the first year of Mr. Xi’s rule, for an organization that offered financial assistance to families of political prisoners. Such programs would be unimaginable in China today. Mr. Guo himself disappeared from public view after being released from nearly a year of detention in 2015.

In a society as tightly controlled as China under Mr. Xi, it is impossible for anyone to have the kind of influence that Mr. Navalny had. The Communist Party’s greatest fear is organizations and individuals that could challenge its rule. That’s why it does not like religious groups or nongovernmental organizations. It fears entrepreneurs who it believes have the financial power and organizational skills to pose a threat to the party.

It snuffs out any spark that could potentially grow into a prairie fire.

Right now it seems to be obsessed with Teacher Li, a social media influencer with a cat avatar. Li Ying is a painter who in 2022 turned his Twitter account into a one-person news hub that informs the Chinese public of news it does not receive from the heavily censored media and internet. This week, he urged his followers in China to unfollow him because police questioned some of them. Within a day, the number of his followers fell to 1.4 million from 1.6 million.

Mr. Li, who lives in Milan, told me last year that he was preparing himself psychologically for the possibility that he could be murdered.

Russia has been learning from China how to exert control over its people in the social media age. It has blocked most major Western platforms except YouTube since its invasion of Ukraine two years ago. With the death of Mr. Navalny, the most prominent opposition figure, it could be difficult for other opposition leaders, mostly in exile, to build up a national following as he did.

No matter the different forms of authoritarianism they face, Russian and Chinese political prisoners share the aspiration that their countries are not doomed and will become normal, democratic and free.

They’re all Navalnys.

Mr. Navalny chose to return to Russia even though he knew he would be arrested. Xu Zhiyong, the legal scholar who is serving 14 years in prison, made a similar choice.

In 2013, he wrote in an essay that between home and prison, he chose the latter. It was a painful choice for him, but he felt he could not not make the decision he did. After he was released from prison in 2017, he said, he was ready to go back again.

“For many years,” he wrote on Jan. 1, 2020, “I’ve been thinking which would be more valuable for my country: staying in jail or remaining out of it.”

A month later, he was arrested again.