The Second Constitutional Era (Ottoman Turkish: ايکنجى مشروطيت دورى; Turkish: İkinci Meşrûtiyyet Devri) was the period of restored parliamentary rule in the Ottoman Empire between the 1908 Young Turk Revolution and the 1920 dissolution of the General Assembly, during the empire's twilight years.

The absolutist rule of Sultan Abdulhamid II had been opposed by the Young Turks, an underground movement of reformists which called for the restoration of constitutional monarchy. In 1908, a faction within the Young Turks called the Committee of Union and Progress (CUP) forced Abdulhamid II to restore the liberal constitution of 1876 and the Ottoman parliament in the Young Turk Revolution. Abdul Hamid had previously suspended the parliament and constitution in 1878, only two years after they had been introduced. Whereas the short First Constitutional Era lacked political parties, the second era initially featured unprecedented political pluralism within the empire and openly contested elections.

The period was marked by political instability as opposition groups attempted to challenge the CUP's dominance and its increasingly repressive tendencies. In 1909, the CUP was briefly expelled from Istanbul during the 31 March Incident, a reactionary uprising sparked by a mutiny of soldiers from the city's garrison. In the aftermath of the crisis, Abdulhamid II was deposed and his brother Mehmed V appointed sultan. The second largest party, the Freedom and Accord Party, remained locked in a power struggle with the CUP and following electoral fraud by the CUP in the 1912 general election its military wing launched a successful coup in July 1912. The CUP regained power in a coup the following year and repressed other opposition parties, effectively establishing a one-party oligarchy led by the "Three Pashas", Talaat Pasha, Enver Pasha, and Cemal Pasha.

The empire was in a perpetual state of crisis as it suffered continual territorial losses: Bulgaria declared independence, Austria-Hungary annexed Bosnia and ethnic conflict in Ottoman Macedonia continued unabated. Italy invaded Ottoman Tripolitania in 1911 and the empire lost the vast majority of its remaining European territory when the Balkan League overran Rumelia in 1912. In 1914, the Ottoman Empire entered World War I and the increasingly radicalised CUP conducted ethnic cleansing and genocide against the empire's Armenian, Assyrian, and Greek citizens, events sometimes collectively referred to as the Late Ottoman genocides. Following the Ottoman surrender in 1918, the CUP leadership fled into exile and the Allies occupied Constantinople. The Ottoman parliament angered the Allies by signing the Amasya Protocol with Turkish revolutionaries in Ankara and agreeing to a Misak-ı Millî (National Pact). As plans for the partition of the Ottoman Empire advanced following the Conference of London, the Allies forced the dissolution of the assembly, thus bringing the Second Constitutional Era to an end. Many parliamentarians would become members of the Grand National Assembly during Turkey's War for Independence, and ultimately continued their careers in the Republic.