<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><Version>2.2.0.25</Version><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><ReportLongName>006090 - Disclosure - Stock-Based Compensation</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelColumn>false</LabelColumn><CurrencyCode>USD</CurrencyCode><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName>1/1/2011 - 3/31/2011
USD ($)

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Incentive Plan&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; TEXT-INDENT: 0pt"&gt;&lt;br /&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman"&gt;On February 25, 2011, the Company granted 382,809 shares of restricted stock and 313,518 stock appreciation rights ("SARs) to employees, which vest in one-third annual increments over a three-year service period.&amp;#160;&amp;#160;The aggregate grant-date fair value of awards expected to vest totaled approximately $22.0 million, which will be amortized on a straight-line basis over a period of 3.0 years from the date of grant.&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; TEXT-INDENT: 0pt"&gt;&lt;br /&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman"&gt;At March 31, 2011, the Company had approximately $39.0 million of unrecognized future stock-based compensation, which is expected to be recognized as compensation expense over a remaining weighted-average period of 2.3 years.&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; TEXT-INDENT: 0pt"&gt;&lt;br /&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-STYLE: italic; FONT-FAMILY: Times New Roman"&gt;LeTourneau Technologies, Inc. Incentive Plan&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; TEXT-INDENT: 0pt"&gt;&lt;br /&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman"&gt;In December 2010, the Company adopted the LeTourneau Technologies, Inc. Incentive Plan, effective January 1, 2011 (the "LeT LTIP"), under which the compensation committee of the board of directors of Rowan (the "Compensation Committee") may grant to LeTourneau employees stock appreciation rights ("LeT SARs") and restricted stock units ("LeT RSUs) denominated in common stock of LeTourneau.&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; TEXT-INDENT: 0pt"&gt;&lt;br /&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman"&gt;LeT SARs confer on the grantee the right to receive cash or shares of LeTourneau, at the discretion of the Compensation Committee, of an amount equal to the excess of the fair market value per share on the exercise date over the fair market value per share on the grant date with respect to a specific number of shares of LeTourneau common stock.&amp;#160;&amp;#160;LeT RSUs are rights to receive cash, or shares of LeTourneau stock at the discretion of the Compensation Committee, equal in value to the fair market value of a specific number of shares of common stock of LeTourneau.&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; TEXT-INDENT: 0pt"&gt;&lt;br /&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman"&gt;On January 1, 2011, LeT SARs and LeT RSUs were awarded to 50 LeTourneau employees with a fair value totaling $5.3 million.&amp;#160;&amp;#160;Fifty percent of the total grant was in the form of LeT SARs, and fifty percent was in the form of LeT RSUs.&amp;#160;&amp;#160;The LeT SARs vest pro rata over a three-year service period and will be settled in cash or stock only after a change in control of LeTourneau other than a spinoff.&amp;#160;&amp;#160;The actual number of LeT RSUs that vest is subject to the progress towards achieving specific LeTourneau performance measures over a one-year performance period.&amp;#160;&amp;#160;The LeT RSUs vest over a three-year period, such that one-third is vested after the performance period is complete (and the adjustment of the award from 75% to 125% depending on achievement of the long-term goals underlying the award), and one-third vests on the second anniversary of the grant, and the final one-third vests on the third anniversary of the grant.&amp;#160;&amp;#160;The LeT RSUs will be settled only upon a change in control; except, however, any vested awards not previously settled due to a change in control within ten years following the grant date shall be settled in cash on the 10&lt;font style="DISPLAY: inline; FONT-SIZE: 70%; VERTICAL-ALIGN: text-top"&gt;th&lt;/font&gt; anniversary of the grant.&amp;#160;&amp;#160;For purposes of the LeT RSUs, unlike the LeT SARS, a spinoff is considered a change in control.&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; TEXT-INDENT: 0pt"&gt;&lt;br /&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman"&gt;Total fair value of $5.3 million, less expected forfeitures, will be amortized over a three-year vesting period. Expense will be recognized for only those awards that actually vest due to satisfying the service requirements and, in the case of the LeT RSUs, for progress towards meeting the performance goals.&lt;/font&gt;&lt;/div&gt;&lt;div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="justify"&gt;&lt;font style="DISPLAY: inline; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman"&gt;&lt;/font&gt;&lt;br /&gt;&amp;#160;&lt;/div&gt;</NonNumbericText><NonNumericTextHeader>Note 9 - Stock-Based Compensation2009 Rowan Companies, Inc. Incentive PlanOn February 25, 2011, the Company granted 382,809 shares of restricted stock and</NonNumericTextHeader><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios></Cell></Cells><OriginalInstanceReportColumns /><Unit>Other</Unit><ElementDataType>us-types:textBlockItemType</ElementDataType><SimpleDataType>string</SimpleDataType><ElementDefenition>Disclosure of compensation-related costs for share-based compensation which may include disclosure of policies, compensation plan details, allocation of stock compensation, incentive distributions, share-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef
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 -Name Statement of Financial Accounting Standard (FAS)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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