Abol Hassan Bani-Sadr, who as the first president of the Islamic Republic of Iran tried and failed to resist the currents of religious radicalism, died on Saturday at the Pitié-Salpêtrière hospital in Paris. He was 88.

His death came after a long illness, his family said on Mr. Bani-Sadr’s official website.

Mr. Bani-Sadr was president when the newborn Islamic Republic went through two of its greatest traumas. Militants stormed the United States embassy in Tehran on Nov. 4, 1979. Ten months later, Saddam Hussein’s army invaded Iran, setting off the horrific Iran-Iraq war.

The revolution’s supreme leader, Ayatollah Ruhollah Khomeini, used these two episodes to purge secularists, nationalists and other moderates from Iran’s government. Mr. Bani-Sadr was the most prominent victim.

Soon after American diplomats were taken hostage at the U.S. embassy, Mr. Bani-Sadr visited the occupiers and urged them to withdraw.

“You think you have taken America hostage,” he told them. “What a delusion! In fact, you have made Iran the hostage of the Americans.”

Several months later, Iran’s ambassador to the United Nations, Mansour Farhang, resigned in protest of his government’s failure to end the crisis and wrote a long article condemning the takeover. A newspaper connected to Mr. Bani-Sadr was the only one in Iran to publish it.

Mr. Farhang, who became a professor of political science at Bennington College, remembered Mr. Bani-Sadr as “a genuinely liberal Muslim.”

“In the position of nominal power for a year and a half, he was more of a preacher and teacher than a manager of power,” Mr. Farhang said in an interview for this obituary in 2013. “Intellectually and temperamentally, he could not function as a politician in an autocratic state.”

Mr. Bani-Sadr was an admirer of Mohammad Mossadegh, who was Iran’s nationalist prime minister in the early 1950s until he was deposed in a coup directed by the C.I.A. He sought to revive Mr. Mossadegh’s political bloc, the National Front, and infuse it with moderate Islam to create a new form of government for Iran.

“Bani-Sadr was active in the early 1960s in the emergence of the second National Front and played a leading role in its student section,” the Iranian American historian Fakhreddin Azimi said in interview for this obituary. “After the revolution, as president in the most unfavorable circumstances, he endeavored to rely on Khomeini’s support and good will, as well as on his own popularity, to ward off or slow down the rise of clerical supremacy.”

“His efforts, given the disarray of broadly secular forces actually or potentially favorable to him and the ability of the clerics to win over Khomeini, were doomed to failure. With the loss of Khomeini’s support, his fate was sealed,” he said.

Mr. Bani-Sadr was born on March 22, 1933, into a family of pious landowners in Hamadan, Iran, said to be one of the world’s oldest towns. After studying law, theology and sociology at Tehran University, he moved to Paris, where he spent several years in the 1960s studying at the Sorbonne. He was caught up in the student movement and led protests against the regime of Shah Mohammed Reza Pahlavi.

Information on Mr. Bani-Sadr’s survivors was not immediately available.

In the 1970s, Mr. Bani-Sadr met Ayatollah Khomeini, a friend of his late father, who had also been a cleric. They were reunited in Paris after Ayatollah Khomeini was exiled there in 1978.

In one of the 20th century’s most spectacular political collapses, the shah fled Iran on Jan. 16, 1979. Ayatollah Khomeini, who had directed the revolution from exile, returned home two weeks later. In the broad-based government that the ayatollah installed, Mr. Bani-Sadr served as deputy minister of finance, then minister of finance, and finally as minister of foreign affairs.

With the ayatollah’s blessing, Mr. Bani-Sadr’s easily won the presidential election of Jan. 25, 1980. The ayatollah, however, had secured approval of a constitution giving him power to dismiss presidents at will. Over the next 18 months, he directed Mr. Bani-Sadr’s rise and fall.

In his first weeks in power, Mr. Bani-Sadr worked to bring order to the shambles that had been left by the collapse of the shah’s government. However, he was quickly was distracted by the hostage crisis.

“The takeover of the U.S. embassy was wholly in line with Khomeini’s strategy of focusing hostility abroad,” he later wrote. “It was at this moment that the idea of a religious state became viable. He also realized that he could now silence people at will, by threatening them with the accusation of being pro-American.”

In the venomous political climate of post-revolution Tehran, enemies rose against Mr. Bani-Sadr. Several of his associates were convicted on trumped-up charges and executed. After war with Iraq broke out, militants criticized him for relying more on the regular army, which they associated with the shah’s monarchy, than on revolutionary guards and other political forces. In the summer and fall of 1980, he survived two helicopter crashes.

The combination of the hostage crisis and the war created a hyper-radical atmosphere in which a tweedy, mustachioed intellectual like Mr. Bani-Sadr could hardly hope to survive. On June 10, 1981, Ayatollah Khomeini removed him from his post as commander in chief. On June 21, parliament ruled him “politically incompetent” and voted to impeach him as president. Ayatollah Khomeini signed the bill the next day.

It accused Mr. Bani-Sadr of “opposing the Islamic Republic; forming an alliance with counterrevolutionary forces attached to the East and the West in order to eliminate the Islamic system; persistent opposition to the Islamic consultative assembly from the outset and even before its inauguration; open interference in the judiciary, incorrect understanding of the most basic tenets of the constitution, and disbelief in the separation of powers.”

By the time of his impeachment, Mr. Bani-Sadr had been in hiding for several days. Six weeks later, he slipped out of the country aboard an air force jet piloted by a sympathetic officer.

For much of his later life, Mr. Bani-Sadr lived with his wife and three children in or near Paris, including at a heavily guarded home in Versailles. He wrote and spoke about his homeland. When signing copies of his memoir, he often added the line, “Elected President of the People of Iran.”

In 1997, Mr. Bani-Sadr testified at a court hearing in Berlin about the assassination of an Iranian dissident there. The court later concluded that senior Iranian leaders had approved the assassination.

After Iranian security forces crushed protests in the wake of the disputed 2009 presidential election, Mr. Bani-Sadr accused the religious regime of “holding on to power solely by means of violence and terror.” He said it had lost both political and religious legitimacy.

“However much he was committed to Islam, he was opposed to a clerical state,” the historian Ervand Abrahamian said in an interview for this obituary. “His tragedy sums up the tragedy of lay intellectuals who thought they could harness religion to nationalism.”