Ball Lightning (Chinese: 球状闪电) is a hard science fiction novel by Chinese author Liu Cixin, also considered a precursor to The Three-Body Problem. The original Chinese language version was published in 2004. In 2018 the English language version, translated by Joel Martinsen, was published in the US by Tor Books.

The novel is set in late 20th and early 21st century China. As a teenager, Chen witnesses his parents be killed by ball lightning. Traumatized but intrigued, he dedicates his life to studying this phenomenon. After training as an atmospheric physicist, he joins a military technology research team alongside PLA major Lin Yun, who aims to develop a ball lightning weapon.

With the help of theoretical physicist Ding Yi, they discover that ball lightning is not a manifestation of lightning. Rather, it is the excited state of a novel macroscopic-sized fundamental particle termed "macro-electron" which, in its ground state, is ubiquitous but near-invisible. After excitation by a high energy source such as a lightning strike, a macro-electron may then release its energy with destructive results, but only against materials that are specific to each macro-electron.

The team successfully captures macro-electrons and creates a weapon that can destroy targeted materials: wood, biological tissue or even microprocessors. The weapon is first deployed against eco-terrorists at a nuclear power plant; excited anti-personnel macro-electrons kill the terrorists and their child hostages, while leaving the plant undamaged. Disillusioned by the lethal application of his work, Chen resigns and returns to civilian research.

After Chen's departure, war erupts between China and its enemies. An attempted ball lightning strike is neutralised by the enemy's countermeasures. Incentivized to develop novel weapons, the ball lightning team also discovers and captures "macro-atomic nuclei", creating the possibility of "macro-fusion," which could release huge amounts of material-selective destructive energy. Fearing the consequences of such technology, the Chinese military terminates macro-fusion research, but Lin Yun defies orders and initiates a test at the cost of her life. The resulting reaction destroys microprocessors across a vast swathe of China, crippling its defence capability. However, China's enemies recognize the potential for macro-fusion to be used for mutual assured destruction, so they sue for peace.

Ding Yi explains to Chen that those "killed" by macro-electrons and macro-fusion instead exist in a quantum state that can occasionally influence the world paranormally. In this manner, an apparition of Lin Yun, who now exists as a quantum entity, converses with her father before vanishing. She later delivers an invisible rose to Chen. A photograph in Ding Yi's apartment displays Lin Yun's new existence among the "dead" child hostages and the animals sacrificed during ball lightning testing.

An American researcher visits Chen, and describes how they had observed several trials where macro-electrons behaved as though observers were present, despite strict no-observer experimental conditions. They hypothesize the existence of extraterrestrial observers.

There were plans to release a film based on the book.