Spencer Perceval Robert Walpole Boleslaus (February 20, 1861 - June 23, 1965), officially referred to as Spencer P.R.W. Boleslaus, widely referred to as Perceval Boleslaus, was a Chawosaurian politician who was a member of the Boleslaus faction of the Bolesław family and he was named after two British Prime Ministers, Spencer Perceval, and Robert Walpole. The uncle and father-in-law of Jonathan Saint Nicholas Boleslaus VI, he attended his daughter's wedding supportively and encouraged her marriage with her cousin.

Like Malcolm Lyons MacKenzie Wilson, and Theodore McClellan, Perceval had a close relationship with Garfield Lucas Webster, both Progressive Republicans, and both Northerners, but Boleslaus and Webster would end up having a strained relationship due to Webster's antisemitism. In 1900, after the Conservatives failed to win the monarchy, the Conservatives had an opposition leadership election, on which Boleslaus lost to Wilson by a narrow margin, Wilson portrayed Boleslaus as a "negro-lover" and a "miscegnationist", these attacks resulted in Boleslaus' narrow defeat.

Boleslaus was struck by family tragedy when three of his daughter's children, Wolfgang, James, and Charlotte, all died before adulthood, leaving his daughter two surviving children, Jonathan and Elisabeth.

Perceval Boleslaus had a personal conflict with Garfield Webster, Webster, because Boleslaus is Slavic, accused Boleslaus of being Jewish, an accusation Boleslaus had always ignored, and throughout his whole premiership, Webster harassed Boleslaus and his family and shamed Boleslaus' daughter over her marriage, telling Elisabeth Boleslaus "now you're living like a real Jew", this offended Boleslaus. When Garfield Webster died in 1955, Boleslaus privately rejoiced, but publicly(and privately) mourned for his family.

On June 23, 1965, Boleslaus died at the age of 104, in New York City, allegedly at his hotel room in the Plaza Hotel. It is unknown where Perceval Boleslaus is laid to rest, or how. The cause of Boleslaus' death is unknown.