A CNN spokesperson said in a brief statement on Thursday that Hill, a professor of media studies at Temple University, was "no longer under contract".
The network did not give a reason, but the move came amid objections to Hill's speech by the Anti-Defamation League (ADL) and other groups.
Hill, a recurring political commentator on CNN, had called for "a single secular democratic state for everyone" in a meeting at the UN marking the International Day of Solidarity with the Palestinian People on Wednesday, with a "free Palestine from the river to the sea".
The ADL said the "river to the sea" phrase was code for the destruction of Israel, adding that the annual UN event promoted "divisiveness and hate".
According to the Jewish Voice for Peace, "while the ADL markets itself as a civil rights organisation, its history betrays an extensive record of anti-Arab, anti-Muslim and anti-Palestinian advocacy".
In 1993, the United States police raided the offices of the ADL in San Francisco and found illegally obtained files on nearly 10,000 individuals and at least 950 organisations, including labour unions, LGBT groups, progressive media, Arab-American organisations, anti-Zionist Jewish organisations and other civil rights groups.
Hill defended his speech in social media posts, saying he did not support anti-Semitism and that his "reference to 'river to the sea' was not a call to destroy anything or anyone".
"It was a call for justice, both in Israel and in the West Bank/Gaza," he tweeted. "The speech very clearly and specifically said those things."
"I support Palestinian freedom. I support Palestinian self-determination. I am deeply critical of Israeli policy and practice," he continued. "I do not support anti-Semitism, killing Jewish people, or any of the other things attributed to my speech."
Politicians, journalists and pro-Palestinian activists called Hill's firing shameful, and accused CNN of kowtowing to right-wing Israeli groups.
"Calling out the oppressive policies in Israel, advocating for Palestinians to be respected, and for Israelis and Palestinians alike to have peace and freedom is not anti-Semitic," said Rashida Tlaib, a Palestinian American congresswoman.
Media personality Mehdi Hasan questioned how CNN could fire Hill while keeping onboard Rick Santorum, who has denied Palestinians exist in the West Bank. Hasan hosts UpFront, a popular news affairs show on Al Jazeera English.
Ayman Mohyeldin, a senior presenter at MSNBC, wrote: "Denying the legitimacy and existence of Palestinians/Palestine/historic Palestine, whether it's on-air commentary, or in official state policy or in simply punditry is widely acceptable among American mainstream media, politicians, and religious figures."