The Man-Kzin Wars is a series of military science fiction short story collections (and is the name of the first collection), as well as the eponymous conflicts between mankind and the Kzinti that they detail (the Kzinti call them the "Wars-With-Men"). They are set in Larry Niven's Known Space universe; however, Niven himself has only written a small number of the stories.

The first story set in the Man-Kzin Wars, The Warriors (1966), was also Niven's first sold story and one of the first of what would become his Known Space series. Niven did not consider himself a good author of war stories; therefore, although a number of his later stories referenced the Man-Kzin Wars, he never actually showed them. However, given that there was a large fan demand for stories covering the conflict, and a number of his author friends had shown interest in writing stories set in the timeframe. Niven therefore allowed the Man-Kzin Wars to become a shared universe, starting with the 1988 release of Man-Kzin Wars.

The series offers an intricate and evolving weave of character development that melds these beings into some of the most complex fictional creatures in any literature, period...
- Quantum, on The Man-Kzin Wars

† Additional Notes:

• "Iron" and "Inconstant Star" were combined as a single collection, Inconstant Star, in 1991.
• "The Children's Hour" and "The Asteroid Queen" were combined as a single collection, The Children's Hour, in 1991.
• "A Darker Geometry" was expanded and republished as a novel in 1996.
• "The Warriors," "Madness Has its Place," "The Man Who Would Be Kzin," and "In the Hall of the Mountain King" were collected as The Best of All Possible Wars in 1998.
• "Cathouse," "Briar Patch," and "The Children's Hour" were collected as The Houses of the Kzinti in 2002.
• Destiny's Forge is a single novel.

The stories appear to be fully canonical in relation the Known Space works by Niven himself. Niven approves each author's request to write a Man-Kzin War story, and also approves the final story (according to his introduction to Man-Kzin Wars IV, he has several times rejected the final story of an author he approved to write).

In many places (such as his Man-Kzin War intros and Playgrounds of the Mind) Niven has praised the work of the authors, and some of his later Man-Kzin War stories (especially Fly-By-Night) have incorporated plot elements from the other authors' stories.

The only part of Niven's work which has contradicted the Man-Kzin Wars stories is the description of the creation of boosterspice in Ringworld's Children, which contradicted the description from The Heroic Myth of Lieutenant Nora Argamentine; however, that also contradicted Niven's earlier descriptions of its creation, and a retcon is possible in that it took several teams combining their work, with some of it being classified by ARM.

Some fans have occasionally questioned certain stories that seem to 'go beyond' the 'realities' of Known Space, such as the mathematical Kzinti from The Heroic Myth of Lieutenant Nora Argamentine or the Puppeteer Guardians from A Darker Geometry. However, no official word from Niven or Baen Books have discounted these stories or their controversial elements.

• Chuut-Riit: Leader of the Kzinti conquest forces
• Buford Early: ARM general known for unorthodox tactics
• Ulf Reichstein Markham: Wunderland resistance leader and ultimate traitor

There are a total of six Man-Kzin Wars. The first began in the mid 2300s. By this time, Human space was in the middle of the "Long Peace." ARM, the United Nations security force, has completely suppressed all 'dangerous' technologies, histories, mental illnesses, and media, leading to not only an end of war and almost all violent crimes, but a change in society so vast that most people have a difficulty even conceptualizing such things.

The UN's reach is limited to Earth, however. There are a number of other colonies in space, the most important being the Asteroid Belt, Wunderland, We Made It, Jinx, and Plateau.

The Kzinti, with vast technical superiority (including gravity drives, telepaths, and a large military empire), detected a human exploration ship in deep space, the Angel's Pencil. After the Kzin telepath learned that the humans were unarmed and didn't even understand the concept of weapons, they attempted to kill the human crew in a slow, painful manner using an inductive heating weapon hoping to capture their ship intact for intelligence purposes. However, one of the humans used the ship's powerful drive system (which doubled as a communications laser) as a weapon and destroyed the Kzin ship, beginning the First Man-Kzin War. The crew then warned Earth of the warlike aliens, although the transmissions were initially dismissed as an outbreak of psychosis. Then a similar encounter between another human ship and Kzin vessel led to the destruction of the more primitive human ship. However, one of the human prisoners, with the aid of a rogue Telepath, was able to escape to the Angel's Pencil and warn them of the danger from their increasing penetration into Kzinti space.

In the course of the First Man-Kzin War the Kzinti invaded and occupied the human colony of Wunderland, in the Alpha Centauri system, using it as a staging point for an attack on Earth. However, the human science-genius Dimity Carmody escaped to the colony world of We Made It. In a replay of first contact, the peaceful humans used communications lasers, fusion drives, and mass drivers to cut the first invasion fleet to ribbons. Over the next several decades, three more fleets were launched against Earth, and all were beaten back. However, after near defeat by the fourth fleet, it was becoming clear to Earth's military leaders that the Kzinti were learning to wage war more effectively than their traditional 'scream and leap' tactics, and that the Solar System's defenses would quickly succumb to the Kzinti's superior numbers, firepower, and technology, were it only wielded with a modicum of tactical and strategic sense. In order to delay the next attack, a Terran Bussard ramjet starship was utilized as a relativistic kill vehicle. Using iron slugs accelerated to 99% of the speed of light, it devastated a portion of the planet, killing humans and Kzinti alike and delaying the launch of yet another Kzin fleet against Earth. A number of specialists traveled aboard this ship, using Stasis fields for lithobraking, and successfully assassinated the Kzin military genius Chuut-Riit who was leading the Kzinti on Wunderland. However, it was only a matter of time until the next assault fleet would come.

At this point, a passing Outsider ship sold the colony of We Made It the secret of hyperdrive, a technology unknown to the Kzinti. Dimity Carmody, the escapee from Wunderland, was instrumental in developing it. Hyperdrive ships were dispatched to Earth, where the faster-than-light drive was used to pre-emptively attack the Fifth Invasion fleet, liberate Wunderland, and go on to attack other Kzinti worlds. The FTL drive allowed the human fleets to coordinate and concentrate their forces beyond anything the Kzinti could manage, even letting them outrun and jam the news of each successive Kzin defeat. The first indication the Kzinti Patriarchy had that much of the Kzin empire was gone and that a significant percentage of all Kzinti had died was when human warships appeared in the skies above their homeworld.

Meanwhile, however, on Wunderland, now liberated by humans, a number of the surviving Kzin, led by Vaemar-Riit, last surviving kitten of Chuut-Riit, and with the co-operation of Dimity Carmody, Nils Rykermann, Leonie Rykermann and other humans, began to cautiously co-operate with humans and try to learn human ways, Vaemar-Riit even enrolling at a human University and obtaining a reserve officer's commission. These became known as the Wunderkzin, and some later proved to be human allies. This slowly growing Man-Kzin co-operation was bitterly opposed both by many other Kzin and by many revanchist humans on Wunderland, while others among the human and kzin communities on Wunderland sought to manipulate the situation for their own ends. There are also on-going human situations - for example Nils Rykermann, a Wunderland academic, in love with dimity Carmody, married Leonie Rykermann, one of his students, during the occupation, believing Dimity to be dead. This situation has not been resolved. There is also a growing relationship between Dimity and Vaemar-Riit which is somewhat ambiguous - the two are depicted together on the cover of Man-Kzin Wars XI.

The war ends in 2433 with the signing of the MacDonald-Rishaii Peace Treaty. The vast majority of the Man-Kzin Wars stories are set just before, during, or just after the First War.

Following the end of hostilities, the Human forces use their hyperdrive ships to initiate a blockade of all Kzinti worlds within range of Human space. The Kzinti of both their homeworld and the prominent colony of W'kkai attempt to begin researching hyperdrive technology in an attempt to break the blockade, with the High Admiral of W'kkai also hoping to overthrow the Patriarch. Due to the treachery of Ulf Reichstein Markham, the Kzinti of Kzin gain access to hyperdrive designs and one familiar with them in 2438.

On Wunderland, an attempt is made to form a stable, democratic government. On Earth, although no one seriously believes the Kzin will stay away, the ARM resorts to its old habits of trying to eliminate all knowledge and technology of war. We Made It continues to create hyperdrives, as the Human military forces attempt to reverse-engineer Kzinti gravity technology. They also attempt to locate and form an anti-Kzin alliance with the Pierin aliens (although according to the Ringworld RPG, the Pierin may already be enslaved at this point).

A troika of officers - Belter General Lucas Fry, Flatlander Major Yankee Clandeboye, and Wunderlander Admiral Blumenhandler - established a semi-covert training center on Barnard's Starbase where unconventional officers devise plans for fighting hyperdrive-equipped Kzinti in the second war, as human tactics in the first were restricted by their own ignorance and by ARM's structure (besides the liberation of Wunderland, only two other planetary assaults, on Down and Hssin, succeeded). They devise two ways to help prepare the rest of the human military: a war game called "Trolls and Bridges," and a book, The Heroic Myth of Lieutenant Nora Argamentine. Written by Clandeboye, they are a fictionalized account of the diary of his cousin, Nora Argamentine, a UN officer caught by Kzinti who later rebelled against them before being gradually lobotomized. The book becomes extremely popular and helps raise morale, as well as the belief that the Kzin will attack again.

All information on the second war comes from the Ringworld RPG guidebook. It begins in 2449 when the Kzinti launch "diversionary raids" on Sigma Draconis and Barnard's Star (which can probably be retconned to due to the Barnard's Starbase from The Heroic Myth of Lieutenant Nora Argamentine) and ends in 2475 with the liberation of the Kdatlyno from Kzin rule.

The Third War is mentioned in the Ringworld RPG and The Ringworld Engineers. According to the game, it started in 2491 and ended in 2531. However, subsequent stories by Niven have apparently made the war end several decade earlier.

At the end of the war, the Wunderland Treatymaker weapon is used on the Kzinti fortress-world of Warhead, creating a huge, habitable canyon on the otherwise Mars-like world. Warhead is annexed by the humans and renamed Canyon.

The Ringworld RPG dates the Fourth War as starting in 2560 and ending in 2584, but like the Third War, later stories have moved those dates back several decades. The war began with Kzinti suicide attacks on Epsilon Eridani. During the war, human adventurers engage in similar suicide attacks on Kzinti harems. The war ends in 2505 with the signing of the Covenant of Shasht (a Kzinti world).

All that is known is that the Fifth War ends sometime near the end of the 26th Century, from a reference in Prisoner of War.

The Sixth and final war is mentioned in Ringworld, Flatlander, and The Soft Weapon. It began around 2600 and lasted for around two decades. During the war, human forces occupied Kzin itself. As part of the peace treaty, humans annexed two Kzinti worlds, including Shasht (renamed Fafnir). Also at the end of the war, the Kzinti Patriarchy is completely and totally disarmed of all military vessels and technology.

Over the next decades and centuries, some Kzinti dream of another war, and go through great lengths (such as piracy, seeking Slaver stasis boxes, and going to Ringworld) to attempt to gain enough of an upper hand to begin one. However, the Kzinti leadership is wise enough to accept that they have been defeated, and another war would be far too costly.

• Timeline of the Known Space universe
• Website for the Man-Kzin Wars novel Destiny's Forge
• Kzinti homepage