Daimyo

 were powerful Japanese magnates, feudal lords who, from the 10th century to the early Meiji period in the middle 19th century, ruled most of Japan from their vast, hereditary land holdings. They were subordinate to the "shōgun" and nominally to the emperor and the kuge. In the term, means "large", and "myō" stands for , meaning "private land".
From the "shugo" of the Muromachi period through the Sengoku to the daimyo of the Edo period, the rank had a long and varied history. The backgrounds of daimyo also varied considerably; while some daimyo clans, notably the Mōri, Shimazu and Hosokawa, were cadet branches of the Imperial family or were descended from the "kuge", other daimyo were promoted from the ranks of the samurai, notably during the Edo period.
Daimyo often hired samurai to guard their land, and they paid the samurai in land or food as relatively few could afford to pay samurai in money. The daimyo era ended soon after the Meiji Restoration with the adoption of the prefecture system in 1871.
"Shugo-daimyo".
The were the first group of men to hold the title daimyo. They arose from among the "shugo" during the Muromachi period. The "shugo-daimyo" held not only military and police powers, but also economic power within a province. They accumulated these powers throughout the first decades of the Muromachi period.
Major "shugo-daimyo" came from the Shiba, Hatakeyama, and Hosokawa clans, as well as the tozama clans of Yamana, Ōuchi, Takeda and Akamatsu. The greatest ruled multiple provinces.
The Ashikaga shogunate required the "shugo-daimyo" to reside in Kyoto, so they appointed relatives or retainers, called "shugodai", to represent them in their home provinces. Eventually some of these in turn came to reside in Kyoto, appointing deputies in the provinces.
The Ōnin War was a major uprising in which "shugo-daimyo" fought each other. During this and other wars of the time, "kuni ikki", or provincial uprisings, took place as locally powerful warriors sought independence from the "shugo-daimyo". The deputies of the "shugo-daimyo", living in the provinces, seized the opportunity to strengthen their position. At the end of the fifteenth century, those "shugo-daimyo" who succeeded remained in power. Those who had failed to exert control over their deputies fell from power and were replaced by a new class, the "sengoku-daimyo", who arose from the ranks of the "shugodai" and "jizamurai".
"Sengoku-daimyo".
Among the were many who had been "shugo-daimyo", such as the Satake, Imagawa, Takeda, Toki, Rokkaku, Ōuchi, and Shimazu. New to the ranks of the daimyo were the Asakura, Amago, Nagao, Miyoshi, Chōsokabe, Hatano, and Oda. These came from the ranks of the "shugodai" and their deputies. Additional "sengoku-daimyo" such as the Mōri, Tamura, and Ryūzōji arose from the "jizamurai". The lower officials of the shogunate and rōnin (Late Hōjō, Saitō), provincial officials (Kitabatake), and "kuge" (Tosa Ichijō) also gave rise to "sengoku-daimyo".
Edo period.
The Battle of Sekigahara in 1600 marked the beginning of the Edo period. "Shōgun" Tokugawa Ieyasu reorganized roughly 200 daimyo and their territories into "han," which were assessed by rice production. Those heading "han" assessed at 10,000 "koku" (50,000 bushels) or more were considered daimyo. Ieyasu also categorized the daimyo according to their relation to the ruling Tokugawa family: the "shinpan" were related to the Tokugawa; the "fudai" had been vassals of the Tokugawa or allies in battle; and the "tozama" had not allied with the Tokugawa before the battle (did not necessarily fight against the Tokugawa).
The "shinpan" were collaterals of Ieyasu, such as the Matsudaira, or descendants of Ieyasu other than in the main line of succession. Several "shinpan", including the Tokugawa of Owari (Nagoya), Kii (Wakayama), and Mito, as well as the Matsudaira of Fukui and Aizu, held large "han".
A few "fudai daimyo", such as the Ii of Hikone, held large "han," but many were small. The shogunate placed many "fudai" at strategic locations to guard the trade routes and the approaches to Edo. Also, many "fudai daimyo" took positions in the Edo shogunate, some rising to the position of "rōjū." The fact that "fudai daimyo" could hold government positions, while "tozama" in general could not, was a main difference between the two.
"Tozama daimyo" held mostly large fiefs far away from the capital, with e.g. the Kaga "han" of Ishikawa Prefecture, headed by the Maeda clan, assessed at 1,000,000 "koku". Other famous "tozama" clans included the Mori of Chōshū, the Shimazu of Satsuma, the Date of Sendai, the Uesugi of Yonezawa, and the Hachisuka of Awa. Initially, the Tokugawa regarded them as potentially rebellious, but for most of the Edo period, marriages between the Tokugawa and the "tozama", as well as control policies such as "sankin-kōtai", resulted in peaceful relations.
Daimyo were required to maintain residences in Edo as well as their fiefs, and to move periodically between Edo and their fiefs, typically spending alternate years in each place, in a practice called "sankin-kōtai".
After the Meiji Restoration.
In 1869, the year after the Meiji Restoration, the daimyo, together with the "kuge," formed a new aristocracy, the "kazoku". In 1871, the han were abolished, and prefectures were established. In this year, around 200 daimyo returned their titles to the emperor, who consolidated their han into 75 prefectures. Their military forces were also demobilized, with the daimyo and their samurai followers pensioned into retirement. The move to abolish the feudal domains effectively ended the daimyo era in Japan. This was effectively carried out through the financial collapse of the feudal-domain governments, hampering their capability for resistance. 
In the wake of the changes, many daimyo remained in control of their lands, being appointed as prefectural governors; however, they were soon relieved of this duty and called en masse to Tokyo, thereby cutting off any independent base of power from which to potentially rebel. Despite this, members of former daimyo families remained prominent in government and society, and in some cases continue to remain prominent to the present day. For example, Morihiro Hosokawa, the former Prime Minister of Japan, is a descendant of the daimyo of Kumamoto.