<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>2115100 - Disclosure - Related Party Transactions</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>D2013Q2YTD</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0000047129</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-01-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="6 Months Ended" /><Label Key="Calendar" Id="1" Label="Jun. 30, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_RelatedPartyTransactionsAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Related Party Transactions [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_RelatedPartyTransactionsDisclosureTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-family:Times New Roman;font-size:10pt;"&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;font-weight:bold;"&gt;Related Party Transactions&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;font-weight:bold;"&gt;Relationship with Hertz Investors,&amp;#160;Inc., Hertz Holdings and the Sponsors&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:8px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;On December&amp;#160;21, 2005, investment funds associated with or designated by:&lt;/font&gt;&lt;/div&gt;&lt;table cellpadding="0" cellspacing="0" style="padding-bottom:8px;font-family:Times New Roman; font-size:10pt;"&gt;&lt;tr&gt;&lt;td style="width:48px;" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:top" rowspan="1" colspan="1"&gt;&lt;div style="line-height:120%;font-size:10pt;padding-left:24px;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;&amp;#8226;&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:top;" rowspan="1" colspan="1"&gt;&lt;div style="line-height:120%;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;Clayton, Dubilier &amp;amp; Rice, Inc., which was succeeded by Clayton, Dubilier &amp;amp; Rice, LLC, or &amp;#8220;CD&amp;amp;R,&amp;#8221;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;&lt;table cellpadding="0" cellspacing="0" style="padding-bottom:8px;font-family:Times New Roman; font-size:10pt;"&gt;&lt;tr&gt;&lt;td style="width:48px;" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:top" rowspan="1" colspan="1"&gt;&lt;div style="line-height:120%;font-size:10pt;padding-left:24px;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;&amp;#8226;&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:top;" rowspan="1" colspan="1"&gt;&lt;div style="line-height:120%;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;The Carlyle Group, or &amp;#8220;Carlyle,&amp;#8221; and&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;&lt;table cellpadding="0" cellspacing="0" style="padding-bottom:8px;font-family:Times New Roman; font-size:10pt;"&gt;&lt;tr&gt;&lt;td style="width:48px;" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:top" rowspan="1" colspan="1"&gt;&lt;div style="line-height:120%;font-size:10pt;padding-left:24px;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;&amp;#8226;&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:top;" rowspan="1" colspan="1"&gt;&lt;div style="line-height:120%;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;Merrill Lynch &amp;amp; Co., Inc., or "Merrill Lynch,"&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;&lt;div style="line-height:120%;padding-bottom:8px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;or collectively the &amp;#8220;Sponsors,&amp;#8221; acquired all of our common stock from Ford Holdings&amp;#160;LLC.&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;Other than as disclosed below, in the six months ended June 30, 2013, there were no material changes to our relationship with Hertz Investors,&amp;#160;Inc., Hertz Holdings or the Sponsors.&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:8px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;In March 2013, the Sponsors sold &lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;color:#000000;text-decoration:none;"&gt;60,050,777&lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt; shares of their Hertz Holdings common stock to Citigroup Global Markets Inc. and Barclays Capital Inc. as the underwriters in the registered public offering of those shares.  In connection with the offering, Hertz Holdings repurchased from the underwriters &lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;color:#000000;text-decoration:none;"&gt;23,200,000&lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt; of the &lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;color:#000000;text-decoration:none;"&gt;60,050,777&lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt; shares of common stock sold by the Sponsors.&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:8px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;In May 2013, the Sponsors sold &lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;color:#000000;text-decoration:none;"&gt;49,800,405&lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt; shares of their remaining Hertz Holdings common stock to Goldman, Sachs &amp;amp; Co. and J.P. Morgan Securities LLC as the underwriters in the registered public offering of those shares.   &lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;As a result of our initial public offering in November 2006 and subsequent offerings in June 2007, May 2009, June 2009, March 2011, December 2012, March 2013 and May 2013, the Sponsors do not own any shares of Hertz Holdings common stock, other than de minimus amounts held from time to time by the Sponsors and their affiliates in the ordinary course of business.&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;On May 15, 2013, Angel L. Morales, a director of Hertz Holdings and its wholly-owned subsidiary Hertz, or the "Companies," notified the Boards of Directors of the Companies that he was resigning as a director of the Companies effective immediately after the Board of Directors meeting held after the 2013 Annual Meeting held on the same day.  Mr. Morales' decision to resign did not involve any disagreement with the Companies, the management of the Companies or the Boards of Directors of the Companies. &lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;font-weight:bold;"&gt;Financing Arrangements with Related Parties&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;Based on the Sponsors' sale of shares in May 2013, none of our outstanding debt at June 30, 2013 was with related parties.  As of December&amp;#160;31, 2012, approximately &lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;color:#000000;text-decoration:none;"&gt;$189.8 million&lt;/font&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt; of our outstanding debt was with related parties.&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:10px;padding-top:10px;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:Arial;font-size:10pt;"&gt;For information on our total indebtedness, see Note 8&amp;#8212;Debt.&lt;/font&gt;&lt;/div&gt;&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 850

 -SubTopic 10

 -Section 50

 -Paragraph 3

 -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39603-107864



Reference 2: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 850

 -SubTopic 10

 -Section 50

 -Paragraph 4

 -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39622-107864



Reference 3: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 850

 -SubTopic 10

 -Section 50

 -Paragraph 1

 -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39549-107864



Reference 4: http://www.xbrl.org/2003/role/presentationRef

 -Publisher SEC

 -Name Regulation S-X (SX)

 -Number 210

 -Section 04

 -Paragraph b

 -Article 3A



Reference 5: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 235

 -SubTopic 10

 -Section S99

 -Paragraph 1

 -Subparagraph (SX 210.4-08.(k))

 -URI http://asc.fasb.org/extlink&amp;oid=6881521&amp;loc=d3e23780-122690



Reference 6: http://www.xbrl.org/2003/role/presentationRef

 -Publisher SEC

 -Name Regulation S-X (SX)

 -Number 210

 -Section 08

 -Paragraph k

 -Article 4



Reference 7: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 850

 -SubTopic 10

 -Section 50

 -Paragraph 6

 -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39691-107864



Reference 8: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 850

 -SubTopic 10

 -Section 50

 -Paragraph 5

 -URI http://asc.fasb.org/extlink&amp;oid=6457730&amp;loc=d3e39678-107864



Reference 9: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Statement of Financial Accounting Standard (FAS)

 -Number 57

 -Paragraph 1-4

 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Related Party Transactions</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>Related Party Transactions</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://www.hertz.com/role/RelatedPartyTransactions</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
