The Wilhelmine period or Wilhelmian era (German: Wilhelminische Zeit, Wilhelminische Epoche) comprises the period of German history between 1888 and 1918, embracing the reign of Kaiser Wilhelm II in the German Empire from the death of Kaiser Friedrich III until the end of World War I and Wilhelm's abdication during the November Revolution.

It represented an era of creative ferment in the society, politics, culture, art, literature, and architecture of Germany. It also roughly coincided with the late Victorian and Edwardian eras in the British Empire, the Gilded Age in the United States, the Belle Époque in the Third French Republic, and the Silver Age in the Russian Empire.

The term "Wilhelminism" (Wilhelminismus) is not meant as a conception of society associated with the name Wilhelm and traceable to an intellectual initiative of the German Emperor. Rather, it relates to the image presented by Wilhelm II and his demeanour, as manifested by the public presentation of grandiose military parades and self-aggrandisement on his part. The latter tendency had already been noticed by his grandfather, Emperor Wilhelm I, while Wilhelm II's father, later Frederick III, was Crown Prince.

Wilhelminism also characterizes the social, literary, artistic, and cultural climate of Wilhelm II's reign, which on the one hand was dominated by the rigidly-conservative opinions of the Prussian Junker aristocracy, those associated with the German Agrarian League, and of the German industrialists, which closely mirrored those of the British upper class during the parallel Victorian era in the British Empire. Ironically, Germany during the Wilhelmian era was, on the other hand, distinguished by escalating secularization and growing belief in progress among intellectuals, in response to recent medical and scientific advances and the enormous prosperity of the heavily-industrialized German Empire, but which was at polar odds with the last Kaiser's belief in both Lutheranism and social conservatism. Even so, Otto von Bismarck's Anti-Socialist Laws were not renewed and the Iron Chancellor's efforts to renew them were the catalyst for his forced resignation at the last Kaiser's insistence.

The final break between the Iron Chancellor and the last Kaiser came when Bismarck initiated discussions with the opposition to form a new parliamentary majority without consulting with the monarch first. The Kartell, the shifting coalition government that Bismarck had been able to maintain since 1867, had finally lost its majority of seats in the Reichstag due to the Anti-Socialist Laws fiasco. The remaining powers in the Reichstag were the Catholic Centre Party and the Conservative Party.

In most parliamentary systems, the head of government depends upon the confidence of the parliamentary majority and has the right to form coalitions to maintain a majority of supporters. In a constitutional monarchy like the German Empire, however, the Chancellor or Prime Minister is required to meet regularly with the monarch to explain his or her policies and intentions within the Government. A Chancellor also could not afford to make an enemy of the monarch, who represented the only real separation of powers and check and balance against a Chancellor's otherwise absolute power. Moreover, a constitutional monarch has plenty of means at his or her disposal of quietly blocking an elected head of state's policy objectives and is one of the only people who can forcibly remove an overly ambitious Chancellor or Prime Minister from power. For these reasons, the last Kaiser believed that he had every right to be informed before Bismarck began coalition talks with the Opposition.

In a deeply ironic moment, a mere decade after expelling religious orders, banning Catholic schools, and demonizing all members of the Catholic Church in Germany as (German: Reichsfeinde, "traitors to the Empire") during the Kulturkampf, Bismarck decided to start coalition talks with the all-Catholic Centre Party. He invited that party's leader in the Reichstag, Baron Ludwig von Windthorst, to meet with him and began the negotiations by offering to overturn the 1872 Jesuit Law in return for the Centre Party's support. The last Kaiser always had a warm relationship with Baron von Windthorst, whose decades long defence of German Catholics, Poles, Jews, and other minorities against government overreach by the Iron Chancellor have since attracted very high praise and comparisons to Irish nationalist statesmen Daniel O'Connell and Charles Stewart Parnell, but Wilhelm was furious to hear about Bismarck's plans for coalition talks with the Centre Party only after they had already begun.

After a heated argument at Bismarck's estate over the latter's alleged disrespect for the Imperial Family, Wilhelm stormed out. Bismarck, forced for the first time in his career into a crisis that he could not twist to his own advantage, wrote a blistering letter of resignation, decrying the Monarchy's involvement in both foreign and domestic policy. The letter was published only after Bismarck's death.