<?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>114 - Disclosure - Line of Credit</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>eol_PE11510---1310-Q0011_STD_182_20130803_0</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0000786110</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-02-03T00:00:00</PeriodStartDate><PeriodEndDate>2013-08-03T00:00:00</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="Aug. 03, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>4</Level><ElementName>ck0000786110_LineOfCreditFacilitiesTextBlock</ElementName><ElementPrefix>ck0000786110_</ElementPrefix><IsBaseElement>false</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="eol_PE11510---1310-Q0011_STD_182_20130803_0" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div&gt;
 &lt;p style="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"&gt;
 &lt;b&gt;6. Line of Credit&lt;/b&gt;&lt;/p&gt;
 &lt;p style="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"&gt;
 We have a senior secured asset-based revolving credit facility,
 which was amended and restated in March 2012 to, among other
 things, lower the interest rate and extend the maturity date (as so
 amended and restated, the &amp;#x201C;ABL&amp;#x201D;). As a result of this
 amendment, we recorded a loss on extinguishment of debt of
 $1.2&amp;#xA0;million during the first quarter of fiscal 2012 for the
 write-off of deferred financing costs related to the ABL. The ABL
 provides senior secured financing of up to $225&amp;#xA0;million,
 subject to a borrowing base. Availability under the ABL is subject
 to the assets of the Company, any subsidiary co-borrowers and any
 subsidiary guarantors that are available to collateralize the
 borrowings thereunder, and is reduced by the level of outstanding
 letters of credit. As of August&amp;#xA0;3, 2013, there was
 $39.9&amp;#xA0;million of commercial and standby letters of credit
 outstanding and no borrowing outstanding. As of August&amp;#xA0;3,
 2013, availability under the ABL was approximately
 $139.4&amp;#xA0;million. There were no borrowings during the 13 and 26
 week periods ended August&amp;#xA0;3, 2013 and July&amp;#xA0;28, 2012.&lt;/p&gt;
 &lt;p style="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"&gt;
 The ABL provides us the right to request up to $125&amp;#xA0;million of
 additional commitments under this facility (or, if less, the amount
 permitted under the Term Loan described in Note 7), subject to the
 satisfaction of certain conditions. Principal amounts outstanding
 under the ABL are due and payable in full in March 2017. Borrowings
 under the ABL bear interest at a rate per annum equal to, at our
 option, either (a)&amp;#xA0;a base rate determined by reference to the
 highest of (1)&amp;#xA0;the prime rate of Bank of America, N.A.,
 (2)&amp;#xA0;the federal funds effective rate plus 0.50% and (3)&amp;#xA0;a
 LIBOR rate determined by reference to the costs of funds for U.S.
 dollar deposits for an interest period of one month adjusted for
 certain additional costs, plus 1.00% or (b)&amp;#xA0;a LIBOR rate
 determined by reference to the costs of funds for U.S. dollar
 deposits for the interest period relevant to such borrowing
 adjusted for certain additional costs (&amp;#x201C;Adjusted
 LIBOR&amp;#x201D;), in each case plus an applicable margin. In addition
 to paying interest on outstanding principal under the ABL, we are
 required to pay a commitment fee on unutilized commitments
 thereunder, which is 0.375%&amp;#xA0;per annum under the amended ABL,
 and was 0.5%&amp;#xA0;per annum prior to March 2012.&lt;/p&gt;
 &lt;p style="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"&gt;
 If at any time the aggregate amount of outstanding loans,
 unreimbursed letter of credit drawings and undrawn letters of
 credit under the ABL exceeds the lesser of (a)&amp;#xA0;the commitment
 amount and (b)&amp;#xA0;the borrowing base, we will be required to
 repay outstanding loans and/or cash collateralize letters of credit
 in an aggregate amount equal to such excess, with no reduction of
 the commitment amount. The ABL contains financial and other
 covenants that, among other things, restrict our ability to incur
 additional indebtedness and pay dividends. As of August&amp;#xA0;3,
 2013, we were in compliance with these covenants. The obligations
 under the ABL are secured, subject to certain exceptions, by
 substantially all of our assets. We and our 100%-owned domestic
 subsidiaries have fully and unconditionally guaranteed our
 obligations under the ABL.&lt;/p&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>Line of Credit Facilities [Text Block]</ElementDefenition><ElementReferences>No definition available.</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Line of Credit</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>Line of Credit</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.gymboree.com/taxonomy/role/NotesToFinancialStatementsLineOfCreditFacilitiesTextBlock</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>1</NumberOfRows></InstanceReport>
