Exhibit 31.1

CERTIFICATION

I, Robert E.
Swanson, certify that:

|   |                                                                                                                                                                                                                                                                                                                                                 
|-- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|1. | I have
 reviewed this annual report on Form 10-K of the Ridgewood Energy S Fund, LLC;                                                                                                                                                                                                                                                           
|   |                                                                                                                                                                                                                                                                                                                                                 
|2. | Based on my knowledge, this report does not contain any untrue
 statement of a material fact or omit to state a material fact necessary to
 make the statements made, in light of the circumstances under which such
 statements were made, not misleading with respect to the period covered by
 this report;                                  
|   |                                                                                                                                                                                                                                                                                                                                                 
|3. | Based on my knowledge, the financial statements, and other
 financial information included in this report, fairly present in all material
 respects the financial condition, results of operations and cash flows of the
 registrant as of, and for, the periods presented in this report;                                                      
|   |                                                                                                                                                                                                                                                                                                                                                 
|4. | The registrants other certifying officer(s) and I are responsible
 for establishing and maintaining disclosure controls and procedures (as
 defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control
 over financial reporting (as defined in Exchange Act Rule s 13a  15(f) and
 15d  15(f)) for the registrant and have:

| |  |                                                                                                                                                                                                                                                                                                                                                                                                 
| |  | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  | (a) Designed
 such disclosure controls and procedures, or caused such disclosure controls
 and procedures to be designed under our supervision, to ensure that material
 information relating to the registrant, including its consolidated
 subsidiaries, is made known to us by others within those entities,
 particularly during the period in which this report is being prepared;         
| |  |                                                                                                                                                                                                                                                                                                                                                                                                 
| |  | (b) Designed
 such internal control over financial reporting, or caused such internal
 control over financial reporting to be designed under our supervision, to
 provide reasonable assurance regarding the reliability of financial reporting
 and the preparation of financial statements for external purposes in
 accordance with generally accepted accounting principles;                
| |  |                                                                                                                                                                                                                                                                                                                                                                                                 
| |  | (c) Evaluate
 the effectiveness of the registrants disclosure controls and procedures and
 presented in this report our conclusions about the effectiveness of the
 disclosure controls and procedures, as of the end of the period covered by
 this report based on such evaluation; and                                                                                                      
| |  |                                                                                                                                                                                                                                                                                                                                                                                                 
| |  | (d)
 Disclosed in this report any change in the registrants internal control over
 financial reporting that occurred during the registrants most recent fiscal
 quarter (the registrants fourth fiscal quarter in the case of an annual
 report) that has materially affected, or is reasonably likely to materially
 affect, the registrants internal control over financial reporting; and

|   |                                                                                                                                                                                                                                                                                                       
|-- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|5. | The registrants other certifying officer(s) and I have disclosed,
 based on our most recent evaluation of internal control over financial
 reporting, to the registrants auditors and the audit committee of the
 registrants board of directors (or persons performing the equivalent
 functions):

| |  |                                                                                                                                                                                                                                                                                  
| |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  | (a) All
 significant deficiencies and material weaknesses in the design or operation
 of internal control over financial reporting which are reasonably likely to
 adversely affect the registrants ability to record, process, summarize and
 report financial information; and
| |  |                                                                                                                                                                                                                                                                                  
| |  | (b) Any
 fraud, whether or not material, that involves management or other employees
 who have a significant role in the registrants internal control over
 financial reporting.                                                                                                

|       |  |                                       
|------ |  | --------------------------------------
|Dated: |  | March 14,
 2008                       
|       |  |                                       
|/s/    |  | ROBERT E.
 SWANSON                    
|Name:  |  | Robert E.
 Swanson                    
|       |  |                                       
|Title: |  | President
 and Chief Executive Officer
|       |  | (Principal
 Executive Officer)        

---