LeBron James is the youngest in a game with 30+ points. He was 18 years and 334 days old against the Grizzlies on November 29, 2003.

youngest player ever to score 30 points in a game
Interpreted as:
youngest player ever to score 30 or more points in a regular-season game
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11/29/2003James12/13/2003James12/19/2003James12/20/2003James12/25/2003James12/28/2003James2/1/2004James2/4/2004James2/20/2004James2/27/2004James11/30/2007Durant12/7/2007Durant3/8/2004James12/12/2007Durant11/30/2018Jackson1/19/2016Booker3/27/2004James4/3/2004James12/14/1997Bryant12/17/1997Bryant3/3/2016Booker3/9/2016Booker3/10/2016Booker3/28/2016Booker18-33418-34818-35418-35518-36018-36319-03319-03619-05219-05919-06219-06919-06919-07419-07619-08119-08819-09519-11319-11619-12519-13119-13219-150
NAMEDATETMOPPAGEPTSMINREBASTSTLBLKTOVFGMFGAFG%3PM3PA3P%FTMFTAFT%PF+/-
LeBron JamesLeBron James11/29/2003CLECLEvsMEMMEM18-3343355167118142850.03650.02366.71-10
LeBron JamesLeBron James12/13/2003CLECLEvsBOSBOS18-348374534002102050.01520.0161888.92-2
LeBron JamesLeBron James12/19/2003CLECLE@PHIPHI18-354364245404142458.35771.433100.01+9
LeBron JamesLeBron James12/20/2003CLECLE@CHICHI18-3553242610224112250.0050.0101283.32+9
LeBron JamesLeBron James12/25/2003CLECLE@ORLORL18-360344726218132846.441040.04580.00-9
LeBron JamesLeBron James12/28/2003CLECLEvsPORPOR18-3633239109305152365.2020.022100.01+11
LeBron JamesLeBron James2/1/2004CLECLE@WASWAS19-033384364026142751.91250.091181.840
LeBron JamesLeBron James2/4/2004CLECLEvsLALLAL19-036324344000122646.244100.04580.00-2
LeBron JamesLeBron James2/20/2004CLECLEvsSASSAS19-0523239112212142360.90044100.00+3
LeBron JamesLeBron James2/27/2004CLECLE@ORLORL19-0593049113315111957.911100.07887.51+7
Kevin DurantKevin Durant11/30/2007SEASEAvsINDIND19-062354052237122060.03560.081266.74+13
Kevin DurantKevin Durant12/7/2007SEASEAvsMILMIL19-06935398105392045.02633.3151693.84+18
LeBron JamesLeBron James3/8/2004CLECLE@ATLATL19-069344567102112347.81425.0111384.61+11
Kevin DurantKevin Durant12/12/2007SEASEA@NYKNYK19-074303554203112055.01520.07887.51+8
Jaren Jackson Jr.Jaren Jackson Jr.11/30/2018MEMMEM@BKNBKN19-076364382001132259.13742.977100.04+13
Devin BookerDevin Booker1/19/2016PHXPHXvsINDIND19-08132400200491656.361154.588100.03-9
LeBron JamesLeBron James3/27/2004CLECLEvsNJNNJN19-0884143613302152951.71250.01010100.01+10
LeBron JamesLeBron James4/3/2004CLECLEvsGSWGSW19-0953446810113122842.93560.071163.61-3
Kobe BryantKobe Bryant12/14/1997LALLALvsDALDAL19-113303233002122157.13742.93475.03+13
Kobe BryantKobe Bryant12/17/1997LALLAL@CHICHI19-116332932000122060.03560.06966.740
Devin BookerDevin Booker3/3/2016PHXPHX@MIAMIA19-125343934004112152.43742.999100.04-8
Devin BookerDevin Booker3/9/2016PHXPHXvsNYKNYK19-131323931003142850.03837.51250.02-25
Devin BookerDevin Booker3/10/2016PHXPHX@DENDEN19-132354435115122450.01520.0101190.93-16
Devin BookerDevin Booker3/28/2016PHXPHX@MINMIN19-150304335014102245.52450.08988.94-4
Kevin Knox IIKevin Knox II1/13/2019NYKNYKvsPHIPHI19-155314470204122352.24944.43475.04+11