<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/schedule13g" xmlns:com="http://www.sec.gov/edgar/common">
<schemaVersion>X0202</schemaVersion>
<headerData>
	<submissionType>SCHEDULE 13G/A</submissionType>
	<previousAccessionNumber>0000312348-26-000013</previousAccessionNumber>
	<filerInfo>
		<filer>
			<filerCredentials>
				<cik>0000312348</cik>
				<ccc>XXXXXXXX</ccc>
			</filerCredentials>
		</filer>
		<liveTestFlag>LIVE</liveTestFlag>


	</filerInfo>
</headerData>
<formData>
	<coverPageHeader>
		<amendmentNo>18</amendmentNo>
		<securitiesClassTitle>Common Stock</securitiesClassTitle>
		<eventDateRequiresFilingThisStatement>03/31/2026</eventDateRequiresFilingThisStatement>
		<issuerInfo>
			<issuerCik>0000350894</issuerCik>
			<issuerName>SEI Investments Co</issuerName>
			<issuerCusips>
				<issuerCusipNumber>784117103</issuerCusipNumber>
			</issuerCusips>
			<issuerPrincipalExecutiveOfficeAddress>
				<com:street1>1 FREEDOM VALLEY DRIVE</com:street1>
				<com:city>OAKS</com:city>
				<com:stateOrCountry>PA</com:stateOrCountry>
				<com:zipCode>19456-1100</com:zipCode>
			</issuerPrincipalExecutiveOfficeAddress>
		</issuerInfo>
		<designateRulesPursuantThisScheduleFiled>
			<designateRulePursuantThisScheduleFiled>Rule 13d-1(d)</designateRulePursuantThisScheduleFiled>
		</designateRulesPursuantThisScheduleFiled>
	</coverPageHeader>
	<coverPageHeaderReportingPersonDetails>

		<reportingPersonName>Loomis, Sayles &amp; Co., L.P.</reportingPersonName>
		<citizenshipOrOrganization>DE</citizenshipOrOrganization>
		<reportingPersonBeneficiallyOwnedNumberOfShares>
			<soleVotingPower>7130873.0</soleVotingPower>
			<sharedVotingPower>0</sharedVotingPower>
			<soleDispositivePower>0</soleDispositivePower>
			<sharedDispositivePower>0</sharedDispositivePower>
		</reportingPersonBeneficiallyOwnedNumberOfShares>
		<reportingPersonBeneficiallyOwnedAggregateNumberOfShares>8683519.78</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
		<classPercent>7.1</classPercent>
		<typeOfReportingPerson>IA</typeOfReportingPerson>
	</coverPageHeaderReportingPersonDetails>
	<items>
		<item1>
			<issuerName>SEI Investments Co</issuerName>
			<issuerPrincipalExecutiveOfficeAddress>1 FREEDOM VALLEY DRIVE, OAKS, PA, 19456-1100</issuerPrincipalExecutiveOfficeAddress>
		</item1>
		<item2>
			<filingPersonName>Loomis, Sayles &amp; Co., L.P.</filingPersonName>
			<principalBusinessOfficeOrResidenceAddress>One Financial Center Boston, MA  02111</principalBusinessOfficeOrResidenceAddress>
			<citizenship>United States</citizenship>
		</item2>
		<item3>
			<notApplicableFlag>N</notApplicableFlag>
			<typeOfPersonFiling>IA</typeOfPersonFiling>
		</item3>
		<item4>
			<amountBeneficiallyOwned>8683519.78</amountBeneficiallyOwned>
			<classPercent>7.1</classPercent>
			<numberOfSharesPersonHas>
				<solePowerOrDirectToVote>7130873.0</solePowerOrDirectToVote>
				<sharedPowerOrDirectToVote>0</sharedPowerOrDirectToVote>
				<solePowerOrDirectToDispose>0</solePowerOrDirectToDispose>
				<sharedPowerOrDirectToDispose>0</sharedPowerOrDirectToDispose>
			</numberOfSharesPersonHas>
		</item4>
		<item5>
			<notApplicableFlag>Y</notApplicableFlag>
			<classOwnership5PercentOrLess>N</classOwnership5PercentOrLess>
		</item5>
		<item6>
			<notApplicableFlag>N</notApplicableFlag>
			<ownershipMoreThan5PercentOnBehalfOfAnotherPerson>Clients of Reporting Person have such a right, none of whom has such interest relating to more than 5% of any class.</ownershipMoreThan5PercentOnBehalfOfAnotherPerson>
		</item6>
		<item7>
			<notApplicableFlag>Y</notApplicableFlag>
		</item7>
		<item8>
			<notApplicableFlag>Y</notApplicableFlag>
		</item8>
		<item9>
			<notApplicableFlag>Y</notApplicableFlag>
		</item9>
		<item10>
			<notApplicableFlag>N</notApplicableFlag>
			<certifications>By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired andare held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect ofchanging or influencing the control of the issuer of the securities and were not acquired and are not held in connection withor as a participant in any transaction having that purpose or effect, other than activities solely in connection with anomination under 240.14a-11. </certifications>
		</item10>
	</items>
	<signatureInformation>
			<reportingPersonName>Loomis, Sayles &amp; Co., L.P.</reportingPersonName>
		<signatureDetails>
			<signature>Mari Shimokawa</signature>
			<title>Deputy Chief Compliance Officer</title>
			<date>05/14/2026</date>
		</signatureDetails>
	</signatureInformation>
</formData>
</edgarSubmission>
